Beneficial Effects of N-Acetyl-L-cysteine or Taurine Pre- or Post-treatments in the Heart, Spleen, Lung, and Testis of Hexavalent Chromium-Exposed Mice.

Hexavalent chromium[Cr(VI)] compounds may induce toxic effects, possibly via reactive intermediates and radicals formed during Cr(VI) reduction. In this study, we probed the possible effects of N-acetyl-L-cysteine (NAC) and taurine pre- or post-treatments on Cr(VI)-induced changes in lipid peroxidation and nonprotein thiols (NPSH) in mice heart, lung, spleen, and testis tissues. The mice were randomly assigned to six groups, consisting of control, Cr(VI)-exposed (20 mg Cr/kg, intraperitoneal ,ip), NAC (200 mg/kg, ip) as pre-treatment and post-treatment, and taurine (1 g/kg, ip) pre-treatment and post-treatment groups. Lipid peroxidation and NPSH levels were determined and the results were compared with regard to tissue- and antioxidant-specific basis. Exposure to Cr(VI) significantly increased lipid peroxidation in all tissues as compared to the control (p < 0.05); and consistent with this data, NPSH levels were significantly decreased (p < 0.05). Notably, administration of NAC and taurine, either before or after Cr(VI) exposure, was able to ameliorate the lipid peroxidation (p < 0.05) in all tissues. In the case of NPSH content, while the decline could be alleviated by both NAC and taurine pre- and post-treatments in the spleen, diverging results were obtained in other tissues. The effects of Cr(VI) on the lung thiols were abolished by pre-treatment with NAC and taurine; however, post-treatments could not exert significant effect. While thiol depletion in the heart was totally replenished by NAC and taurine administrations, NAC pre-treatment was partially more effective than post-treatment. In contrast with lipid peroxidation data, NAC treatment could not provide a statistically significant beneficial effect on NPSH content of the testis, whereas the effect in this tissue by taurine was profound. Thus, these data highlight the importance of tissue-specific factors and the critical role of administration time. Overall, our data suggest that NAC and taurine may have potential in prevention of Cr(VI)-induced toxicity in the heart, lung, spleen, and testis tissues.

The thiosemicarbazone Me2NNMe2 induces paraptosis by disrupting the ER thiol redox homeostasis based on protein disulfide isomerase inhibition.

Due to their high biological activity, thiosemicarbazones have been developed for treatment of diverse diseases, including cancer, resulting in multiple clinical trials especially of the lead compound Triapine. During the last years, a novel subclass of anticancer thiosemicarbazones has attracted substantial interest based on their enhanced cytotoxic activity. Increasing evidence suggests that the double-dimethylated Triapine derivative Me2NNMe2 differs from Triapine not only in its efficacy but also in its mode of action. Here we show that Me2NNMe2- (but not Triapine)-treated cancer cells exhibit all hallmarks of paraptotic cell death including, besides the appearance of endoplasmic reticulum (ER)-derived vesicles, also mitochondrial swelling and caspase-independent cell death via the MAPK signaling pathway. Subsequently, we uncover that the copper complex of Me2NNMe2 (a supposed intracellular metabolite) inhibits the ER-resident protein disulfide isomerase, resulting in a specific form of ER stress based on disruption of the Ca2+ and ER thiol redox homeostasis. Our findings indicate that compounds like Me2NNMe2 are of interest especially for the treatment of apoptosis-resistant cancer and provide new insights into mechanisms underlying drug-induced paraptosis.

Blocking the Thiol at Cysteine-322 Destabilizes Tau Protein and Prevents Its Oligomer Formation.

Abnormal accumulation of tau protein into oligomers contributes to neuronal dysfunction. Reduction of tau level is potentially able to prevent its accumulation. Here we uncover a critical role of the free thiol at Cys-322 in determining tau stability. We found that the application of thiol-blocking agents like NEM or MMTS blocks this thiol, by which it destabilizes tau protein and prevents its oligomer formation. Furthermore, we identified a tau-interacting protein, selenoprotein W, which attenuates tau accumulation by forming disulfide linkage between SelW Cys-37 and tau Cys-322. These findings provide a promising strategy to prevent tau accumulation and oligomer formation.

HIV-1 tat expression and sulphamethoxazole hydroxylamine mediated oxidative stress alter the disulfide proteome in Jurkat T cells.

BACKGROUND: Adverse drug reactions (ADRs) are a significant problem for HIV patients, with the risk of developing ADRs increasing as the infection progresses to AIDS. However, the pathophysiology underlying ADRs remains unknown. Sulphamethoxazole (SMX) via its active metabolite SMX-hydroxlyamine, when used prophylactically for pneumocystis pneumonia in HIV-positive individuals, is responsible for a high incidence of ADRs. We previously demonstrated that the HIV infection and, more specifically, that the HIV-1 Tat protein can exacerbate SMX-HA-mediated ADRs. In the current study, Jurkat T cell lines expressing Tat and its deletion mutants were used to determine the effect of Tat on the thiol proteome in the presence and absence of SMX-HA revealing drug-dependent changes in the disulfide proteome in HIV infected cells. Protein lysates from HIV infected Jurkat T cells and Jurkat T cells stably transfected with HIV Tat and Tat deletion mutants were subjected to quantitative slot blot analysis, western blot analysis and redox 2 dimensional (2D) gel electrophoresis to analyze the effects of SMX-HA on the thiol proteome. RESULTS: Redox 2D gel electrophoresis demonstrated that untreated, Tat-expressing cells contain a number of proteins with oxidized thiols. The most prominent of these protein thiols was identified as peroxiredoxin. The untreated, Tat-expressing cell lines had lower levels of peroxiredoxin compared to the parental Jurkat E6.1 T cell line. Conversely, incubation with SMX-HA led to a 2- to 3-fold increase in thiol protein oxidation as well as a significant reduction in the level of peroxiredoxin in all the cell lines, particularly in the Tat-expressing cell lines. CONCLUSION: SMX-HA is an oxidant capable of inducing the oxidation of reactive protein cysteine thiols, the majority of which formed intermolecular protein bonds. The HIV Tat-expressing cell lines showed greater levels of oxidative stress than the Jurkat E6.1 cell line when treated with SMX-HA. Therefore, the combination of HIV Tat and SMX-HA appears to alter the activity of cellular proteins required for redox homeostasis and thereby accentuate the cytopathic effects associated with HIV infection of T cells that sets the stage for the initiation of an ADR.

Design and synthesis of γ-butyrolactone derivatives as potential spermicidal agents.

A series of γ-butyrolactone derivatives has been designed and synthesized from commercially available 2-acetyl butyrolactone (3-acetyldihydrofuran-2(3H)-one, 1) by aminoalkylating its active methylene followed by condensation with different aldehydes. Compounds having amino group were further converted to their respective tartrate salts and were evaluated for spermicidal activity against human sperm in vitro. Compounds showing appreciable spermicidal activity at ⩽0.5% [3c, 4d (0.5%); 2c, 3d (0.1%); 2d, 4c (0.05%)] were tested for safety studies against human cervical (HeLa) cell line. These compounds were found safer than, Nonoxynol-9. One of the two most active compounds was also found to be the safest (IC50=961 µg/ml; 4c), while the second compound exhibited lower safety against HeLa (IC50=269 µg/ml; 2d). The compound 4c significantly reduced the number of free thiols on human sperm. All the compounds were inactive against Trichomonas vaginalis.

Conversion of S-phenylsulfonylcysteine residues to mixed disulfides at pH 4.0: utility in protein thiol blocking and in protein-S-nitrosothiol detection.

A three step protocol for protein S-nitrosothiol conversion to fluorescent mixed disulfides with purified proteins, referred to as the thiosulfonate switch, is explored which involves: (1) thiol blocking at pH 4.0 using S-phenylsulfonylcysteine (SPSC); (2) trapping of protein S-nitrosothiols as their S-phenylsulfonylcysteines employing sodium benzenesulfinate; and (3) tagging the protein thiosulfonate with a fluorescent rhodamine based probe bearing a reactive thiol (Rhod-SH), which forms a mixed disulfide between the probe and the formerly S-nitrosated cysteine residue. S-Nitrosated bovine serum albumin and the S-nitrosated C-terminally truncated form of AdhR-SH (alcohol dehydrogenase regulator) designated as AdhR*-SNO were selectively labelled by the thiosulfonate switch both individually and in protein mixtures containing free thiols. This protocol features the facile reaction of thiols with S-phenylsulfonylcysteines forming mixed disulfides at mild acidic pH (pH = 4.0) in both the initial blocking step as well as in the conversion of protein-S-sulfonylcysteines to form stable fluorescent disulfides. Labelling was monitored by TOF-MS and gel electrophoresis. Proteolysis and peptide analysis of the resulting digest identified the cysteine residues containing mixed disulfides bearing the fluorescent probe, Rhod-SH.

Efflux of glutathione and glutathione complexes from human erythrocytes in response to inorganic arsenic exposure.

The objective of the present study was to investigate if arsenic exposure results in glutathione efflux from human erythrocytes. Arsenite significantly depleted intracellular nonprotein thiol level in a time- and concentration-dependent manner. The intracellular nonprotein thiol level was decreased to 0.767 ± 0.0017 µmol/ml erythrocyte following exposure to 10 mM of arsenite for 4 h. Extracellular nonprotein thiol level was increased concomitantly with the intracellular decrease and reached to 0.481 ± 0.0005 µmol/ml erythrocyte in 4 h. In parallel with the change in extracellular nonprotein thiol levels, significant increases in extracellular glutathione levels were detected. Extracellular glutathione levels reached to 0.122 ± 0.0013, 0.226 ± 0.003, and 0.274 ± 0.004 µmol/ml erythrocyte with 1, 5, and 10 mM of arsenite, respectively. Dimercaptosuccinic acid treatment of supernatants significantly increased the glutathione levels measured in the extracellular media. Utilization of MK571 and verapamil, multidrug resistance-associated protein 1 and Pgp inhibitors, decreased the rate of glutathione efflux from erythrocytes suggesting a role for these membrane transporters in the process. The results of the present study indicate that human erythrocytes efflux glutathione in reduced free form and in conjugated form or forms that can be recovered with dimercaptosuccinic acid when exposed to arsenite.

Gastroprotection of suaveolol, isolated from Hyptis suaveolens, against ethanol-induced gastric lesions in Wistar rats: role of prostaglandins, nitric oxide and sulfhydryls.

Hyptis suaveolens is a medicinal plant that is, according to traditional medicine, considered useful in the treatment of gastric ulcers. Although its gastroprotective activity was reported, the active compounds have not been identified. Therefore, the aim of the present study was to identify at least one active compound potentially responsible for the gastroprotective activity of H. suaveolens by using a bioassay guided study with an ethanol-induced gastric ulcer experimental model in rats. The results show that the hexane extract had protective activity (close to 70% when using doses between 10 and 100 mg/kg), and that the compound suaveolol, isolated from this extract, was one of the active gastroprotective agents. This is the first report about the gastroprotective activity of suaveolol. Rats treated with this compound at 3, 10, 30 and 100 mg/kg showed 12.6, 21.3, 39.6 and 70.2% gastroprotection respectively. The effect elicited by suaveolol (at 100 mg/kg) was attenuated by pretreatment with either N(G)-nitro-L-arginine methyl ester (70 mg/kg, i.p.), a nitric oxide (NO) synthase inhibitor, indomethacin (10 mg/kg, s.c.), a blocker of prostaglandin synthesis, or N-ethylmaleimide (10 mg/kg, s.c.), a blocker of sulfhydryl groups. This suggests that the gastroprotective mechanism of action of this compound involves NO, prostaglandins and sulfhydryl groups.

[Population-related peculiarities of molecular stress-responsive systems of bivalve mollusk under the effect of tetrazine pesticide].

Tetrazine pesticides are widely used for the treatment of crops in most EU countries and USA. However, data about the effect of environmentally realistic concentrations of biocides on the molecular stress response system in non-target organisms are absent. The aim of our study was the comparison of adaptive capability of bivalve mollusk Anodonta cygnea from two populations under the effects of commercial pesticide Apollo in terms of biochemical parameters of the digestive gland. The differences between parameters of oxidative stress and glutathione transferase activity in specimens of control groups from clean (I group) and polluted (B group) areas have been shown. Under the effect of Apollo, the level of protein carbonyls and microsomal oxidation processes increased, and the level of metallothioneins and oxyradical formation decreased in the specimens from both populations. However, the treatment provoked the activation of antioxidant processes in the I group and their inhibition in B group. Potentially the injury of cellular thiols, glutathione and metallothioneins, seems to be key point of tetrazine pesticides toxicity.

Involvement of glutathione, sulfhydryl compounds, nitric oxide, vasoactive intestinal peptide, and heat-shock protein-70 in the gastroprotective mechanism of Croton cajucara Benth. (Euphorbiaceae) essential oil.

This study aimed to evaluate the gastroprotective mechanism of action of the essential oil of Croton cajucara Benth. (Euphorbiaceae) stem bark in ethanol-induced gastric ulcers and its in vitro anti-Helicobacter pylori activity. The involvement of heat-shock protein-70, vasoactive intestinal peptide, glutathione, nitric oxide, and nonprotein sulfhydryl compounds in the gastroprotective effect was determined in male Wistar rats. The minimum inhibitory concentration against H. pylori was determined in vitro. The results were analyzed by analysis of variance followed by the Dunnett test, and a P value less than 0.05 was considered to represent a statistically significant difference. C. cajucara decreased ethanol-induced ulcer area in 100% of ulcers and decreased the histologic lesions. In the C. cajucara group, the area marked by heat-shock protein-70 was significantly higher than the area in the control group; this finding was not seen for vasoactive intestinal peptide. C. cajucara could not maintain glutathione levels close to those in the sham group. The gastric ulcer area of rats treated with the sulfhydryl compound blocker was decreased, but the ulcer area of rats treated with nitric oxide synthase inhibitor showed no alteration. The minimum inhibitory concentration obtained for C. cajucara was 125 µg/mL. These findings suggest that sulfhydryl compounds and heat-shock protein-70, but not nitric oxide, glutathione, or vasoactive intestinal peptide, are involved in the C. cajucara gastroprotective effect against ethanol-induced gastric ulcers.

Tea catechin EGCg suppresses the mgl gene associated with halitosis.

Epigallocatechin gallate (EGCg), the main antimicrobial tea catechin, has been reported to inhibit growth and virulence factors of oral pathogens in vitro. Although the mechanism is unclear, the potential of EGCg in reducing halitosis caused by volatile sulfur compounds (VSCs) has been suggested. This study tested the hypothesis that EGCg reduces VSCs by suppressing mgl, the gene encoding L-methionine-α-deamino-γ-mercaptomethane-lyase, responsible for methyl mercaptan (CH3SH) production by oral anaerobes. In this study, the effect of EGCg on in vitro growth, CH3SH production, and mgl gene expression in P. gingivalis W83 was investigated. EGCg inhibited growth of P. gingivalis W83 (MIC = 97.5 µg/mL) and was bactericidal (MBC = 187.5 µg/mL). At sub-MIC levels, EGCg inhibited CH3SH production, and mgl mRNA and protein expression (p < 0.05). We conclude that EGCg may represent a natural and alternative agent to the antimicrobial chemicals currently available for halitosis control.

Contribution of exofacial thiol groups in the reducing activity of Lactococcus lactis.

Lactococcus lactis can decrease the redox potential at pH 7 (E(h7)) from 200 to -200 mV in oxygen free Man-Rogosa-Sharpe media. Neither the consumption of oxidizing compounds or the release of reducing compounds during lactic acid fermentation were involved in the decrease in E(h7) by the bacteria. Thiol groups located on the bacterial cell surface appear to be the main components that are able to establish a greater exchange current between the Pt electrode and the bacteria. After the final E(h7) (-200 mV) was reached, only thiol-reactive reagents could restore the initial E(h7) value. Inhibition of the proton motive force showed no effect on maintaining the final E(h7) value. These results suggest that maintaining the exofacial thiol (-SH) groups in a reduced state does not depend on an active mechanism. Thiol groups appear to be displayed by membrane proteins or cell wall-bound proteins and may participate in protecting cells against oxidative stress.

Bioassay-guided isolation of an anti-ulcer chromene from Eupatorium aschenbornianum: role of nitric oxide, prostaglandins and sulfydryls.

Eupatorium aschenbornianum is considered useful in the treatment of gastric ulcer. In the current study the validity of this practice was tested by using the experimental model of an ethanol induced gastric ulcer in rats. The results show that E. aschenbornianum had gastroprotective activity, that the hexane extract had the highest protective activity (85.65+/-4.76%), and that encecanescin isolated from this extract was the main active gastroprotective agent. The effect elicited by encecanescin was attenuated by N(G)-nitro-L-arginine methyl ester, N-ethylmaleimide and indomethacin, which suggests that NO, prostaglandins and sulfydryl groups are involved in the mechanisms of gastroprotective action.

The role of low molecular weight thiols in T lymphocyte proliferation and IL-2 secretion.

Glutathione (GSH) is an abundant intracellular tripeptide that has been implicated as an important regulator of T cell proliferation. The effect of pharmacological regulators of GSH and other thiols on murine T cell signaling, proliferation, and intracellular thiol levels was examined. l-Buthionine-S,R-sulfoximine (BSO), an inhibitor of GSH synthesis, markedly reduced GSH levels and blocked T cell proliferation without significant effect on cell viability. N-acetylcysteine markedly enhanced T cell proliferation without affecting GSH levels. Cotreatment of T cells with N-acetylcysteine and BSO failed to restore GSH levels, but completely restored the proliferative response. Both 2-ME and l-cysteine also reversed the BSO inhibition of T cell proliferation. Intracellular l-cysteine levels were reduced with BSO treatment and restored with cotreatment with NAC or l-cysteine. However, 2-ME completely reversed the BSO inhibition of proliferation without increasing intracellular cysteine levels. Therefore, neither GSH nor cysteine is singularly critical in limiting T cell proliferation. Reducing equivalents from free thiols were required because oxidation of the thiol moiety completely abolished the effect. Furthermore, BSO did not change the expression of surface activation markers, but effectively blocked IL-2 and IL-6 secretion. Importantly, exogenous IL-2 completely overcame BSO-induced block of T cell proliferation. These results demonstrate that T cell proliferation is regulated by thiol-sensitive pathway involving IL-2.

Effect of a triclosan/PVM/MA copolymer/fluoride dentifrice on volatile sulfur compounds in vitro.

OBJECTIVE: The objective of the investigation was to document the in vitro efficacy of a triclosan/PVM/MA copolymer/fluoride (TCF) dentifrice against the formation of volatile sulfur compounds (VSC) as well as the growth of H2S-producing bacteria. Clinical studies using organoleptic judges, gas chromatography, or a portable sulfide monitor have generally been employed in the assessment of treatments for the control of oral malodor. However, these studies are not appropriate for screening purposes because of the expense and time required. METHODS: An in vitro method was developed for the purpose of screening new compounds, agents or formulations for their ability to control VSC formation and for determining bio-equivalence of efficacy when implementing changes in existing formulations. The method combines basic microbiological methods, dynamic flow cell techniques and head space analysis. The in vitro VSC method was validated by comparing the efficacy of two dentifrices containing TCF with a control fluoride dentifrice as the TCF products have been clinically proven to control oral malodor. RESULTS: In the validation studies, the TCF-containing dentifrices were significantly better (P < 0.05) than the control dentifrice in inhibiting VSC formation and reducing H(2)S-producing bacteria. For example, when compared with baseline, the TCF dentifrices reduced VSC formation between 42 and 49% compared with the control dentifrice which reduced VSC formation 3%. There was no significant difference (P > 0.05) between the two TCF dentifrice formulations. CONCLUSION: Using an in vitro breath VSC model, it has been demonstrated that two variants of a dentifrice containing triclosan, PVM/MA copolymer and fluoride have efficacy that is significantly better than a control fluoridated dentifrice and that there is no significant difference between the triclosan/PVM/MA copolymer/fluoride dentifrice variants.

Tumor necrosis factor-alpha mediates osteopenia caused by depletion of antioxidants.

We recently found that estrogen deficiency leads to a lowering of thiol antioxidant defenses in rodent bone. Moreover, administration of agents that increase the concentration in bone of glutathione, the main intracellular antioxidant, prevented estrogen-deficiency bone loss, whereas depletion of glutathione by buthionine sulfoximine (BSO) administration provoked substantial bone loss. It has been shown that the estrogen-deficiency bone loss is dependent on TNFalpha signaling. Therefore, a model in which estrogen deficiency causes bone loss by lowering antioxidant defenses predicts that the osteopenia caused by lowering antioxidant defenses should similarly depend on TNFalpha signaling. We found that the loss of bone caused by either BSO administration or ovariectomy was inhibited by administration of soluble TNFalpha receptors and abrogated in mice deleted for TNFalpha gene expression. In both circumstances, lack of TNFalpha signaling prevented the increase in bone resorption and the deficit in bone formation that otherwise occurred. Thus, depletion of thiol antioxidants by BSO, like ovariectomy, causes bone loss through TNFalpha signaling. Furthermore, in ovariectomized mice treated with soluble TNFalpha receptors, thiol antioxidant defenses in bone remained low, despite inhibition of bone loss. This suggests that the low levels of antioxidants in bone seen after ovariectomy are the cause, rather than the effect, of the increased resorption. These experiments are consistent with a model for estrogen-deficiency bone loss in which estrogen deficiency lowers thiol antioxidant defenses in bone cells, thereby increasing reactive oxygen species levels, which in turn induce expression of TNFalpha, which causes loss of bone.

Mechanism of action of the antifibrogenic compound gliotoxin in rat liver cells.

Gliotoxin has been shown to promote a reversal of liver fibrosis in an animal model of the disease although its mechanism of action in the liver is poorly defined. The effects of gliotoxin on activated hepatic stellate cells (HSCs) and hepatocytes have therefore been examined. Addition of gliotoxin (1.5 microM) to culture-activated HSCs resulted in its rapid accumulation, resulting in increased levels of glutathione and apoptosis without any evidence of oxidative stress. In contrast, although hepatocytes also rapidly sequestered gliotoxin, cell death only occurred at high (50-microM) concentrations of gliotoxin and by necrosis. At high concentrations, gliotoxin was metabolized by hepatocytes to a reduced (dithiol) metabolite and glutathione was rapidly oxidized. Fluorescent dye loading experiments showed that gliotoxin caused oxidative stress in hepatocytes. Antioxidants--but not thiol redox active compounds--inhibited both oxidative stress and necrosis in hepatocytes. In contrast, HSC apoptosis was not affected by antioxidants but was potently abrogated by thiol redox active compounds. The adenine nucleotide transporter (ANT) is implicated in mitochondrial-dependent apoptosis. HSCs expressed predominantly nonliver ANT isoform 1, and gliotoxin treatment resulted in a thiol redox-dependent alteration in ANT mobility in HSC extracts, but not hepatocyte extracts. In conclusion, these data suggest that gliotoxin stimulates the apoptosis of HSCs through a specific thiol redox-dependent interaction with the ANT. Further understanding of this mechanism of cell death will aid in finding therapeutics that specifically stimulate HSC apoptosis in the liver, a promising approach to antifibrotic therapy.

Albumin influences total plasma antioxidant capacity favorably in patients with acute lung injury.

OBJECTIVE: To ascertain the influence of albumin on antioxidant status in patients with acute lung injury. DESIGN: Prospective, randomized, placebo-controlled study. SETTING: Intensive care units, teaching hospitals. PATIENTS: Twenty patients meeting the American European Consensus criteria for acute lung injury. INTERVENTIONS: Ten patients received albumin (25 g of a 25% solution every 8 hrs for a total of nine doses) and ten received placebo (normal saline administered in identical fashion and volume). All received supportive therapy appropriate for patients with acute lung injury. Plasma samples were obtained sequentially from all patients before, 30 mins after, and 4 hrs after albumin/placebo administration. MEASUREMENTS AND MAIN RESULTS: Serum albumin and total protein, total antioxidant status, iron-binding antioxidant protection, iron-oxidizing antioxidant protection, lipid hydroperoxides, protein carbonyls, and plasma thiols were measured. Albumin administration increased plasma albumin concentrations (p <.05 compared with placebo) and decreased concentrations of protein carbonyls (p <.05 compared with placebo). By contrast, plasma lipid hydroperoxide concentrations were similar in both groups, both in absolute terms and relative to albumin content. For all other variables, no significant differences were apparent. For all patients, there was a positive correlation between albumin and plasma thiol concentrations (r =.983, p <.01) and albumin and antioxidant capacity (r =.885, p =.01). In the albumin treatment group, there was a strong correlation between thiols and antioxidant capacity (r =.876, p =.01). No such correlation was apparent in the placebo group. Plasma iron-binding antioxidant protection was negatively correlated (r = -.741, p <.05) with albumin content in the treatment group but not the placebo group. CONCLUSIONS: In patients with acute lung injury, albumin administration favorably influences plasma thiol-dependent antioxidant status as well as levels of protein oxidative damage.

Mechanisms of cytotoxicity of nicotine in human periodontal ligament fibroblast cultures in vitro.

The use of tobacco products significantly contributes to the progression of periodontal disease and poor response to healing following periodontal therapy. The purpose of this study was to determine the effects of nicotine, a major component of cigarette smoking, on human periodontal ligament fibroblast (PDLF) growth, proliferation, and protein synthesis to elucidate its role in periodontal destruction associated with its use. Human PDLFs were derived from three healthy individuals undergoing extraction for orthodontic reasons. At a concentration higher than 2.5 mM, nicotine was found to be cytotoxic to human PDLFs (P < 0.05). Nicotine also significantly inhibited cell proliferation and decreased protein synthesis in a dose-dependent manner. At concentrations of 50 and 200 microM, nicotine suppressed the growth of PDLFs by 48% and 86% (P < 0.05), respectively. A 10-mM concentration level of nicotine significantly inhibited the protein synthesis to only 44% of these in the untreated control (P < 0.05). Furthermore, the effects of antioxidants (superoxide dismutase (SOD); catalase and 2-oxothiazolidine-4-carboxylic acid (OTZ) and buthionine sulfoximine (BSO) were added to search for the possible mechanism of action, as well as a method for the prevention, of cigarette smoking-associated periodontal diseases. The addition of OTZ, a precursor of cysteine that metabolically promotes GSH synthesis, acted as a protective effect on the nicotine-induced cytotoxicity. However, SOD and catalase did not decrease the nicotine-induced cytotoxicity. In contrast, the addition of BSO, a cellular GSH synthesis inhibitor, enhanced the nicotine-induced cytotoxicity. These results indicate that thiol depletion could be the mechanism for nicotine cytotoxicity. The levels of nicotine tested inhibited cell growth, proliferation, and protein synthesis on human PDLFs. This suggests that nicotine itself might augment the destruction of periodontium associated with cigarette smoking. In addition, these inhibitory effects were associated with intracellular thiol levels. Factors that induce glutathione synthesis of human PDLF may be used for further chemoprevention of cigarette smoking-related periodontal diseases.