Cranberry juice extract, a mild prooxidant with cytotoxic properties independent of reactive oxygen species.

A cranberry juice extract (CJE), rich in proanthocyanidins, had weak prooxidant properties, generating low levels of hydrogen peroxide (H2O2) and superoxide. Generation of H2O2 was pH dependent, increasing at alkaline pH, and was lowered in the presence of catalase and, to a lesser extent, of superoxide dismutase (SOD). Growth inhibition and cytotoxicity were noted towards human oral carcinoma HSC-2 cells, with midpoint cytotoxicity at 200 µg/mL CJE, but not towards human gingival HF-1 fibroblasts. Being a mild prooxidant, CJE toxicity was unaffected by exogenous catalase and pyruvate, scavengers of H2O2, but triggered intracellular synthesis of reduced glutathione, as confirmed by cell staining with Cell Tracker™ Green. The presence of exogenous SOD potentiated the toxicity of CJE, possibly by stabilizing the CJE phenols and hindering their degradative autooxidation. Conversely, 'spent' CJE, i.e. CJE added to cell culture medium and incubated for 24 h at 37 °C prior to use, was much less toxic to HSC-2 cells than was freshly prepared CJE. These differences in toxicity between SOD-stabilized CJE, freshly prepared CJE, and 'spent' CJE were confirmed in HSC-2 cells stained with aceto-orcein, which also indicated that the mode of cell death was by the induction of apoptosis.

Choice of DMEM, formulated with or without pyruvate, plays an important role in assessing the in vitro cytotoxicity of oxidants and prooxidant nutraceuticals.

There is much interest in the positive health effects of nutraceuticals, in particular, polyphenols, which have both antioxidant and prooxidant characteristics. Pyruvate, a scavenger of hydrogen peroxide, is a component in some, but not in all, commercial formulations of cell culture media, Dulbecco's modified Eagle's medium in particular. This study showed that the cytotoxicities to human fibroblasts of hydrogen peroxide, tert-butyl hydroperoxide, and various prooxidant nutraceuticals were lessened in Dulbecco's modified Eagle's medium formulated with pyruvate, as compared to the same medium but formulated without pyruvate. Intracellular glutathione was unaffected in cells treated with hydrogen peroxide in Dulbecco's modified Eagle's medium formulated with pyruvate, as compared to medium formulated without pyruvate. In these studies, intracellular glutathione was analyzed in acid-soluble cell extracts by determining the oxidation of reduced glutathione by 5,5'-dithiobis(2-nitrobenzoic acid) to glutathione disulfide, with the formation of the yellow chromagen, 5-thio-2-nitrobenzoic acid, measured spectrophotometrically at 412 nm and by the visualization of reduced glutathione in cells stained with the fluorescent dye, Cell Tracker Green 5-chloromethylfluorescein diacetate. A survey of various cell culture media, formulated with and without pyruvate, confirmed that the level of added hydrogen peroxide was greatly lessened in those media formulated with pyruvate. This study suggested that the pyruvate status of Dulbecco's modified Eagle's medium be specified in the experimental design, especially in studies involving oxidative stress.

In vitro cytotoxicity of (-)-catechin gallate, a minor polyphenol in green tea.

The cytotoxicity of (-)-catechin gallate (CG), a minor polyphenolic constituent in green tea, towards cells derived from tissues of the human oral cavity was studied. The sequence of sensitivity to CG was: immortalized epithelioid gingival S-G cells>tongue squamous carcinoma CAL27 cells>salivary gland squamous carcinoma HSG cells>>normal gingival HGF-1 fibroblasts. Further studies focused on S-G cells, the cells most sensitive to CG. The response of the S-G cells to CG was dependent on the length of exposure, with midpoint cytotoxicity values of 127, 67 and 58muM CG for 1-, 2- and 3-day exposures, respectively. The sequence of sensitivity of the S-G cells to various green tea catechins was characterized as follows: CG, epicatechin gallate (ECG)>epigallocatechin gallate (EGCG)>epigallocatechin (EGC)>>epicatechin (EC), catechin (C). The cytotoxicity of CG, apparently, was not due to oxidative stress as it was a poor generator of H(2)O(2) in tissue culture medium, had no effect on the intracellular glutathione level, its cytotoxicity was unaffected by catalase, and it did not induce lipid peroxidation. However, CG did enhance Fe(2+)-induced, lipid peroxidation. CG-induced apoptosis was detected by nuclear staining, both with acridine orange and by the more specific TUNEL procedure. The lack of caspase-3 activity in cells exposed to CG and the detection of a DNA smear, rather than of discrete internucleosomal DNA fragmentation, upon agarose gel electrophoresis, suggest, possibly, that the mode of cell death was by a caspase-independent apoptotic pathway. The overall cytotoxicity of CG was similar to its epimer, ECG and both exhibited antiproliferative effects equivalent to, or stronger than, EGCG, the most abundant catechin in green tea.

Glutathione as a mediator of the in vitro cytotoxicity of a green tea polyphenol extract.

ABSTRACT The 24-hr cytotoxicities of a green tea polyphenol (GTP) extract to cell lines derived from the human oral cavity were assessed using the neutral red (NR) assay. The sequence of sensitivity was carcinoma HSC-2 cells > immortalized gingival GT1 fibroblasts > normal gingival HGF-2 fibroblasts. The GTP extract generated hydrogen peroxide (H(2)O(2)) in cell culture medium and in phosphate buffer, albeit to a lesser extent. A 3-hr exposure to the GTP extract lowered the intracellular glutathione (GSH) content of the HSC-2 cells, but stimulated that of the GT1 and HGF-2 fibroblasts. The cytotoxicity of a 4-hr exposure of the GTP extract to the HSC-2 and GT1, but not to the HGF-2, cells was lessened in the presence of 2.5 mM GSH. Conversely, a 0.5 hr preexposure to the glutathione depleter, 1-chloro-2-dinotrobenzene (CDNB) at 25 muM, potentiated the 24-hr cytotoxicity of the GTP extract to the HSC-2 and GT1, but not to the HGF-2, cells. Using a cell-free system, it was shown that the GTP extract quickly depleted GSH, with depletion greatly enhanced at an alkaline pH, thus, correlating with the enhanced generation of H(2)O(2) by the GTP extract observed at alkaline pH. Apparently, a mode of cytotoxicity of the GTP extract, in particular to the carcinoma HSC-2 cells, was to induce oxidative stress, as noted by the generation of H(2)O(2), the depletion of intracellular GSH, the protection afforded by extracellular GSH, and cell hypersensitivity after pretreatment with CDNB.

In vitro cytotoxicity of a theaflavin mixture from black tea to malignant, immortalized, and normal cells from the human oral cavity.

The growth inhibitory effects of a theaflavin mixture from black tea were more pronounced to malignant (CAL27; HSC-2; HSG1) and immortalized (S-G; GT1) cells than to normal (HGF-2) cells from the human oral cavity. Studies with malignant carcinoma CAL27 cells and immortalized GT1 fibroblasts showed that cytotoxicity of the theaflavin mixture was enhanced as the exposure time was increased, with the tumor CAL27 cells more sensitive than the GT1 cells. Hydrogen peroxide (H(2)O(2)) was detected in cell culture medium amended with the theaflavin mixture. The level of H(2)O(2) in cell culture medium amended with the theaflavin mixture was lessened in the presence of catalase and CoCl(2); the level of authentic H(2)O(2) was also lessened in the presence of CoCl(2), suggesting that Co(2+) led to the rapid catalytic decomposition of H(2)O(2). The cytotoxicity of the theaflavin mixture was due, in part, to the generation in the cell culture medium of H(2)O(2), which lessened the intracellular levels of glutathione in the CAL27 cells and, to a lesser extent, in the GT1 cells. For both cell types, coexposures of the theaflavin mixture with catalase or CoCl(2) afforded protection.

Differential in vitro cytotoxicity of (-)-epicatechin gallate (ECG) to cancer and normal cells from the human oral cavity.

This study evaluated the biologic activity of epicatechin gallate (ECG), a polyphenol in tea, to carcinoma HSC-2 cells and normal HGF-2 fibroblasts cells from the human oral cavity. The relative cytotoxicity of ECG, as compared to five other polyphenols in tea, was evaluated. For the HSC-2 carcinoma cells, ECG, catechin gallate (CG), and epigallocatechin gallate (EGCG) grouped as highly toxic, epigallocatechin (EGC) as moderately toxic, and catechin (C) and epicatechin (EC) as least toxic. For the HGF-2 fibroblasts, ECG and CG grouped as highly toxic, EGCG as moderately toxic, and EGC, C, and EC as least toxic. The cytotoxic effects of the polyphenols were more pronounced to the carcinoma, than to the normal, cells. The addition of ECG to cell culture medium led to the generation of hydrogen peroxide (H2O2). However, ECG, as compared to EGCG, was a poor generator of H2O2 and, hence, the cytotoxicity of ECG was unaffected by the presence of the antioxidants, N-acetyl cysteine and glutathione, and catalase. The cytotoxicity of ECG was unaffected by a metabolic activating system, i.e., a hepatic microsomal S-9 mix. DNA fragmentation, caspase-3 activity, and nuclear staining, both with acridine orange and the TUNEL procedure, were used to assess ECG-induced apoptosis. ECG induced apoptosis in the carcinoma HSC-2 cells, but not in the normal HGF-2 fibroblasts. This research supports those studies suggesting that tea green is an effective chemopreventive agent of oral carcinoma.

Mediation of the in vitro cytotoxicity of green and black tea polyphenols by cobalt chloride.

The effects of Co2+ (as CoCl2) on the cytotoxicity of green tea polyphenol (GTP) and black tea polyphenol (BTP) extracts towards proliferation of immortalized human gingival epithelial-like S-G cells were studied. The 24 h potencies of GTP and BTP extracts, as determined with the neutral red (NR) cell viability assay, were greatly reduced in the presence of 250, but not of 50, microM Co2+. The cytotoxicities of the GTP and BTP extracts were due, in part, to their generation of hydrogen peroxide (H2O2) in the cell culture medium (DMEM). Progressively increasing the concentration of Co2+ in the tea polyphenol-amended cell culture medium resulted in a lowering of the level of H2O2. The cytotoxicity of freshly added H2O2 to S-G cells was abolished in the presence of 250 microM Co2+ and the level of freshly added H2O2 to cell culture medium was progressively lowered as the concentration of Co2+ was increased. Apparently, under the conditions of these studies, the decreases in the cytotoxicity of GTP and BTP extracts in the presence of CoCl2 were due to the rapid catalytic decomposition by Co2+ of the H2O2 generated in the tea polyphenol-amended cell culture medium.

In vitro cytotoxic and anti-inflammatory effects of myrrh oil on human gingival fibroblasts and epithelial cells.

Limited scientific studies suggest that myrrh (Commiphora molmol) has antibacterial and anti-inflammatory activities. This study determined myrrh oil (MO) cytotoxicity to human gingival fibroblasts and epithelial cells and its effect, measured by ELISA, on interleukin (IL)-1beta-stimulated IL-6 and IL-8 production. Cell viability and cytotoxicity were determined by metabolic reduction of a tetrazolium salt to a formazan dye (MTT assay) and by release of lactate dehydrogenase (LDH) from membrane damaged (LDH release assay) cells, respectively. Based on the MTT assay, 24- and 48-h exposures to /=0.005%, maximally decreased viability of all cell lines. In the LDH release assay, exposure to /=0.0025% MO caused maximal cytotoxicity; /=0.0025% MO, probably reflective of loss of viability. At subtoxic MO levels (0.00001-0.001%), there was a significant reduction of IL-1beta-stimulated IL-6 and IL-8 production by fibroblasts, but not by epithelial cells.

In vitro cytotoxicity to human cells in culture of some phenolics from olive oil.

The neutral red in vitro cytotoxicity assay was used to evaluate the comparative responses of human cells isolated from tissues of the oral cavity to olive oil phenolics. The cell lines used included normal gingival fibroblasts, immortalized, nontumorigenic gingival epithelial cells, and carcinoma cells from the salivary gland. No differences in the relative sensitivities to the phenolics amongst the three cell types were noted. In general, for all cell types, the sequence of increasing cytotoxicity was: oleuropein aglycone>oleuropein glycoside, caffeic acid>o-coumaric acid>cinnamic acid>>tyrosol, syringic acid, protocatechuic acid, vanillic acid. Cytotoxicity was noted only at phenolic concentrations far exceeding those attainable after habitual consumption, thus indicating that consumption of phenol-rich olive oil is safe.

In vitro response of human gingival epithelioid S-G cells to minocycline.

Minocycline, a broad-spectrum antibiotic used in the treatment of acne and periodontal disease and to control inflammatory diseases such as rheumatoid arthritis, has recently been shown to induce a spectrum of adverse health effects. In the light of these contradictory data, this research was directed to provide basic information on the toxicology of minocycline, using in vitro cell culture models, and to evaluate its efficacy in periodontal therapies, particularly for wound healing. The human gingival epithelioid S-G cell line was used as the bioindicator. The greater toxicity of minocycline over doxycycline and tetracycline, related antimicrobial agents, probably correlated with its higher lipophilicity. The cytotoxicity of minocycline was unaffected by an S9 hepatic microsomal fraction, indicating that it is a direct-acting, rather than a metabolism-mediated, cytotoxicant. In comparative toxicity studies, much variation in the degree of sensitivity to minocycline was noted for different cell types. No correlation in the extent of sensitivity to minocycline and the physiologic state of the bioindicator cell (normal, transformed or malignant) was noted. The toxicity of minocycline to the S-G cells was dependent on its concentration and length of exposure. For a continuous 3-day exposure of the S-G cells to minocycline, the midpoint cytotoxicity (or, NR(50)) value, as quantified in the neutral red (NR) assay, was 204 microg/ml on day 1, 84 microg/ml on day 2, and 59 microg/ml on day 3. For a 1-h exposure of the S-G cells in phosphate buffered saline (PBS), the NR(50) value was 780 microg/ml minocycline. Although a 1-h exposure in PBS to 200 microg/ml minocycline exerted some toxicity, the S-G cells recovered on exposure to growth medium; irreversible, progressive damage occurred at 400 microg/ml minocycline and greater. Minocycline, at 50 microg/ml, enhanced attachment of the S-G cells to a gelatin-coated surface and cell migration towards an immobilized fibronectin gradient, both biologic parameters important in periodontal wound healing. Minocycline generally had little or no effect on production of the pro-inflammatory cytokines, interleukin-6 (IL-6) and interleukin-8 (IL-8), by non-activated S-G cells, the exception being stimulation of IL-6 at 48 h. IL-1beta, however, greatly stimulated IL-6 and IL-8 production, which was further increased by concurrent exposure to minocycline. This suggested that minocycline may enhance the ability of gingival epithelial cells to participate in the early, inflammatory phase of periodontal wound healing. The limitation of minocycline efficacy to a rather narrow window of concentration, centering about 50 microg/ml, and primarily for short-term exposures may possibly explain, in part, the contradictory clinical data on the health effects of this drug.

In vitro cytotoxicity of glyco-S-nitrosothiols. a novel class of nitric oxide donors.

The cytotoxicities of the nitric oxide (NO) donors, S-nitroso-N-acetylpencillamine (SNAP) and three glyco-SNAPs, glucose-1-SNAP, glucose-2-SNAP, and fructose-1-SNAP, towards the human gingival epithelioid S-G cell line and three human carcinoma cell lines derived from tissues of the oral cavity were compared using the neutral red (NR) assay. In general, the glucose-SNAPs were more cytotoxic than SNAP, which, in turn, was more cytotoxic than fructose-1-SNAP. Further studies focused on the response of S-G cells to glucose-2-SNAP. The cytotoxicity of glucose-2-SNAP was attributed to NO, as glucose-2-SNAP (t1/2=20 h at 28 degrees C) aged for 4 days was nontoxic, toxicity was eliminated in the presence of hydroxocobalamin, a specific NO scavenger, and toxicity was not noted with glucose-2-AP (the parent compound used to construct glucose-2-SNAP). Exposure of cells to glucose-2-SNAP resulted in a lessening of the intracellular level of glutathione and cells pretreated with the glutathione-depleter, 1,3-bis-(chloroethyl)-1-nitrosourea, were more sensitive to a subsequent challenge with glucose-2-SNAP. Cytotoxicity of glucose-2-SNAP was lessened upon coexposure with the antioxidants, myricetin, N-acetyl-L-cysteine, and L-ascorbic acid. S-G cells exposed to glucose-2-SNAP exhibited bi- and multinucleation. Death of S-G cells exposed to glucose-2-SNAP apparently occurred by apoptosis, as demonstrated with fluorescence microscopy by the appearance of brightly stained, hypercondensed chromatin in spherical cells and of membrane blebbing and by the DNA-ladder of oligonucleosome-length fragments noted with gel electrophoresis. In comparison with other classes of NO donors the sequence of toxicity towards S-G cells was S-nitrosoglutathione>glucose-SNAPs>SNAP, sodium nitroprusside>spermine NONOate>DPTA NONOate>DETA NONOate>fructose-1-SNAP>>SIN-1.

Indirect cytotoxicity of dental materials: a study with Transwell inserts and the neutral red uptake assay.

A modification of the Transwell insert methodology was evaluated by using the neutral red uptake (NRU) assay in a cytotoxicity test. The Transwell insert methodology was developed to assess the biocompatibility of solid materials used in dentistry and, when initially designed, used the release of radiochromium ((51)Cr) in the cytotoxicity assay. Another aim of this study was to evaluate different exposure regimes with which to assess cytotoxicity. The exposure regimes included: a 1-hour exposure in buffer followed by a 24-hour incubation in growth medium; a 2-hour exposure in buffer followed by a 24-hour incubation in growth medium; a 24-hour exposure in serum-limited medium; and a 24-hour exposure in a serum-sufficient medium. The bioindicator target was the Smulow-Glickman (S-G) human gingival cell line and the biomaterials were dental restoratives. The Transwell insert methodology with the NRU cytotoxicity assay as the cytotoxicity endpoint was effective in differentiating the potencies of the dental restoratives; a 2-hour exposure in buffer and a 24-hour exposure in serum-limited medium were the exposure regimes that most clearly differentiated the test agents according to their potencies. The sequence of cytotoxicity of the dental restoratives to the S-G cells was Vitremer > Ketac-Molar Aplicap > Flow-It.

In vitro response of human gingival epithelial S-G cells to resveratrol.

WST-1 (mitochondrial dehydrogenase activities). Arrest of cell growth, due to inhibition of DNA synthesis, may explain the leveling of toxicity between day 2 and 3 for a 3-day continuous exposure to resveratrol. Irreversible damage to cell proliferation was noted in S-G cells exposed to 75-150 microM resveratrol for 2 days and then subsequently maintained for another 3 days in resveratrol-free medium. The cytotoxicity of resveratrol was neither potentiated nor ameliorated in the presence of an hepatic S9 microsomal fraction. The cytotoxicity of hydrogen peroxide to S-G cells was lessened by N-acetyl-L-cysteine and quercetin, but not by resveratrol. For nitric oxide, only N-acetyl-L-cysteine reduced toxicity. The ability of resveratrol to function as an antioxidant was, therefore, not noted under these test conditions.

In vitro cytotoxicity of the nitric oxide donor, S-nitroso-N-acetyl-penicillamine, towards cells from human oral tissue.

The cytotoxicity of the nitric oxide donor, S-nitroso-N-acetyl-penicillamine (SNAP), towards cultured human cells from oral tissue was evaluated. The toxicity of SNAP to Smulow-Glickman gingival epithelial cells was correlated with the liberation of nitric oxide, as N-acetyl-D,L-penicillamine, the SNAP metabolites, N-acetyl-D,L-penicillamine disulfide and nitrite, and preincubated (denitrosylated) SNAP did not affect viability. Comparing equimolar concentrations of various nitric oxide donors, cytotoxicity appeared to be inversely related to the relative stability (i.e., half-life) of the test compound; the sequence of cytotoxicity for a 4 hr exposure was S-nitrosoglutathione>>spermine NONOate> SNAP>DPTA NONOate>>DETA NONOate. Intracellular reduced glutathione (GSH) was lowered in S-G cells exposed to SNAP. Pretreatment of the cells with the GSH depleter, 1,3-bis-(chloroethyl)-1-nitrosourea (BCNU), enhanced the toxicity of SNAP Similar findings of enhanced sensitivity to SNAP were noted with gingival fibroblasts and periodontal ligament cells pretreated with BCNU. The toxicity of SNAP towards the gingival epithelial cells was decreased by cotreatment with the antioxidants, N-acetyl-L-cysteine, L-ascorbic acid, and (+)-catechin. Cells exposed to SNAP exhibited nuclear aberrations, including multilobed nuclei and multinucleation. SNAP-induced cell death was apparently by apoptosis, as noted by fluorescence microscopy and DNA agarose gel electrophoresis.

Triclosan: cytotoxicity, mode of action, and induction of apoptosis in human gingival cells in vitro.

The in vitro cytotoxicology of triclosan, the active ingredient in some mouthrinses and dentifrices used in the prevention and treatment of gingivitis and plaque, was studied using the Smulow-Glickman (S-G) human gingival epithelial cell line. The 24 h midpoint cytotoxicity value was 0.05-0.06 mM triclosan as assessed with the neutral red (NR) assay. Triclosan is used in dentifrices in combination with either zinc citrate or sodium fluoride (NaF). The sequence of potencies of these test agents, as assessed with the NR assay, was triclosan>zinc citrate>>NaF; combinations of triclosan + zinc citrate and triclosan + NaF were additive in their toxicities. Damage to the integrity of the plasma membrane, as assessed by the leakage of lactic acid dehydrogenase during a 3-h exposure, was initially evident with 0.1 mM triclosan. When exposed to triclosan for 3 d, a lag in the growth kinetics of the S-G cells was first observed at 0.01 mM triclosan. A reduction in attachment of S-G cells to dentin chips, previously exposed to triclosan for 1 h, was noted at 0.25 mM triclosan and greater. Triclosan-induced cell death was apparently by apoptosis, as noted by fluorescence microscopy and DNA agarose gel electrophoresis of extracted oligonucleosomal fragments.

In vitro toxicity of sodium nitroprusside to human endothelial ECV304 cells.

The cytotoxicity of sodium nitroprusside (SNP) to the human endothelial cell line, ECV304, was studied. The cytotoxicity of SNP was primarily related to the liberation of nitric oxide (NO). S-nitroso-N-acetyl-d-penicillamine (SNAP), an NO donor, was highly toxic. Other degradation products of SNP either exerted much less toxicity (i.e. cyanide and nitrite) or were non-toxic (i.e. ferricyanide and ferrocyanide). SNP induced multinucleation, inhibited cell proliferation, lowered the endogenous level of reduced glutathione (GSH), and induced apoptotic cell death. The plasma membrane was not the prime site of toxic action, as leakage of lactic acid dehydrogenase (LDH) occurred only at a relatively high concentration of SNP. Cells treated with non-toxic levels of the glutathione-depleting agents, 1-chloro-2,4-dinitrobenzene (CDNB), dl-buthionine-[S,R]-sulfoximine (BSO), and 1,3-bis-(chloroethyl)-1-nitrosourea (BCNU), were hypersensitive to subsequent exposure to SNP. The GSH status of the cells was, therefore, a key factor in determining the cytotoxicity of SNP.

Sodium lauryl sulfate and triclosan: in vitro cytotoxicity studies with gingival cells.

Triclosan and sodium lauryl sulfate (SLS) are antimicrobial agents used, both singularly and in combination, in dentifrices and mouth-rinses. Studies by Waaler et al. (Scand. J. Dent. Res. 101 (1993) 192-195) with human volunteers showed that the adverse side-effects induced by SLS in mouth-rinses, i.e. desquamation of oral epithelium and a burning sensation, were lessened by the addition of triclosan. However, Baert et al. (Int. J. Exp. Pathol. 77 (1996) 73-78) showed that triclosan did not protect the hamster cheek pouch mucosa from irritation caused by SLS. The studies presented herein further evaluated, using a cell culture system, the triclosan-SLS interaction. The in vitro cytotoxicities of triclosan and SLS, alone and in combination, were determined with human gingival S-G epithelial cells and GF fibroblasts. The 24-h midpoint (NR50) cytotoxicity values towards the S-G cells were 0.052 mM triclosan and 0.0075% SLS and for the GF fibroblasts the respective values were 0.095 mM triclosan and 0.0127% SLS. Both agents at their NR50 values induced vacuolization. Coexposures of triclosan and SLS were additive in their cytotoxicities towards the S-G epithelial cells and GF fibroblasts. Pretreatment with triclosan potentiated the toxicity of a subsequent exposure of SLS to the S-G cells; a similar pretreatment of the GF fibroblasts with triclosan had no effect on a subsequent challenge with SLS.

Cytotoxicity of sanguinarine chloride to cultured human cells from oral tissue.

The in vitro cytotoxicity of sanguinarine chloride, a dental product used in the treatment of gingivitis and plaque, was compared using cell lines and primary cells from oral human tissues. For the established cell lines, sanguinarine chloride exhibited similar potencies to S-G gingival epithelial cells and to KB carcinoma cells, whereas HGF-1 gingival fibroblasts were more tolerant. However, a gingival primary cell culture was more sensitive to sanguinarine chloride than were the established cell lines. Detailed studies were performed with the S-G cells. The 24-hr midpoint (NR50) cytotoxicity value towards the S-G cells was 7.6 microM, based on the neutral red cytotoxicity assay; vacuolization and multinucleation were noted. When exposed to sanguinarine chloride for 3 days, a lag in growth kinetics was first observed at 1.7 microM. Damage to the integrity of the plasma membrane was evident, as leakage of lactic acid dehydrogenase occurred during a 3 hr exposure to sanguinarine chloride at 0.1275 mM and greater. The cytotoxicity of sanguinarine chloride to the S-G cells was lessened in the presence of an S9 hepatic microsomal fraction from Aroclor-induced rats or by including fetal bovine serum (15%) in the exposure medium. Progressively increasing the pH from 6.0 to 7.8 enhanced the potency of sanguinarine chloride, presumably due to the enhanced uptake of the lipophilic alkanolamine form, as compared to that of the cationic iminium form.

Benzoyl peroxide cytotoxicity evaluated in vitro with the human keratinocyte cell line, RHEK-1.

The human keratinocyte cell line, RHEK-1, was used to evaluate the cytotoxicity of benzoyl peroxide (BZP). As determined with the neutral red (NR) cytotoxicity assay, the 24-h midpoint (NR50) toxicity values, in mM, were 0.11 for BZP and 29.5 for benzoic acid, the stable metabolite of BZP. Irreversible cytotoxicity occurred after a 1-h exposure to 0.15 mM BZP and greater. When exposed to BZP for 7 days, a lag in growth kinetics was first observed at 0.06 mM BZP. Damage to the integrity of the plasma membrane was evident, as leakage of lactic acid dehydrogenase occurred during a 4-h exposure to BZP at 0.05 mM and greater. Intracellular membranes were also affected, as extensive vacuolization, initially perinuclear but then spreading throughout the cytoplasm, was noted in BZP-stressed cells. The generation of reactive free radicals from BZP was suggested by the following: the intracellular content of glutathione was lowered in cells exposed to BZP; cells pretreated with the glutathione-depleting agent, chlorodinitrobenzene, were hypersensitive to a subsequent challenge with BZP; lipid peroxidation by BZP was inducible in the presence of Fe2+; and cells previously maintained in a medium amended with vitamin E, an antioxidant, were more resistant to BZP, showed less lipid peroxidation in the presence of BZP+Fe2+ and did not develop the extensive intracellular vacuolization as compared to non-vitamin E maintained cells.

An in vitro study on the cytotoxicity of chlorhexidine digluconate to human gingival cells.

Chlorhexidine digluconate is the active ingredient in mouthrinses used to prevent dental plaque and gingivitis. The in vitro cytotoxicity of chlorhexidine was evaluated with the Smulow-Glickman (S-G) gingival epithelial cell line. The potency of chlorhexidine was dependent on the length of exposure and composition of the exposure medium. The midpoint cytotoxicity values for 1-, 24-, and 72-h exposures were 0.106, 0.011, and 0.0045 mmol/L, respectively. S-G cells exposed for 2 h to chlorhexidine and then maintained for 48 h in chlorhexidine-free medium were unable to recover from the initial insult. The adverse effects of chlorhexidine on the plasma membrane were suggested by the leakage of lactic acid dehydrogenase from chlorhexidine-treated S-G cells and by the increased permeability of chlorhexidine-treated liposomes to Ca2+. The toxicity of a 24-h exposure to chlorhexidine to the S-G cells was progressively lessened as the content of fetal bovine serum (FBS) in the exposure medium was increased from 2% to 8%. The potency of a 1-h exposure to chlorhexidine was reduced in medium amended with albumin, lecithin, and heat-killed Escherichia coli. These reductions in toxicity were presumably due to the binding of the cationic chlorhexidine to the negatively charged chemical moieties of the components of FBS and of albumin and lecithin and of sites on the surfaces of bacteria. Combinations of chlorhexidine and carbamide peroxide were additive in their cytotoxicities.