Comparative subchronic oral toxicity of sulphite and acetaldehyde hydroxysulphonate in rats

The Role of Acetylcholine on the Effects of Different Doses of Sulfite in Learning and Memory

In this study, the effects of different doses of sulfite on learning, memory, and long term potentiation as well as the relationship of these effects with acetylcholine pathways, Arc and synapsin 1 levels were investigated. Sixty male Wistar albino rats were randomly divided into three groups as control, S100, and S260. Sodiummetabisulfite (S100;100 mg/kg/day, S260;260 mg/kg/day) was given by oral administration. Behavioral changes were evaluated. After long term potentiation recordings from the perforant pathway-dentate gyrus synapses, animals were sacrificed. Acetylcholinesterase activity, choline acetyltransferase activity, acetylcholine level as well as Arc and Synapsin 1 expressions were analyzed on the hippocampi. The total distance and average velocity values in the open field and Morris water maze tests increased in the sulfite groups, while the discrimination index in the novel object recognition test decreased compared to controls. Acetylcholine levels and choline acetyltransferase activity were also increased in the sulfite groups, while acetylcholinesterase activity was decreased compared to controls. Sulfite intake attenuated long term potentiation in the hippocampus. It has been observed that the excitatory postsynaptic potential slope and population spike amplitude of the field potentials obtained in sulfite groups decreased. This impairment was accompanied by a decrease in Arc and synapsin 1 expressions. In conclusion, it has been shown that sulfite intake in adults impairs learning and memory, possibly mediated by the cholinergic pathway. It is considered that the decrement in Arc and synapsin expressions may play a role in the mechanism underlying the impairment in long term potentiation caused by toxicity.

Sulphur dioxide ameliorates colitis related pathophysiology and inflammation

Colitis is an inflammatory disease of the gastrointestinal tract. Inflammation, oxidative stress and cell death constitute the backbone of colitis. Most of the drugs prescribed for inflammatory bowel disease (IBD) have various side effects. In this scenario, we would like to determine the therapeutic role sulphur dioxide, a gaso-transmitter produced through the metabolism of cysteine in colitis. Colitis was induced through intrarectal administration of 2,4,6-trinitrobenzenesulfonic acid (TNBS) in male Wistar rats. Rats were administered with 0.9% saline containing Na₂SO₃ and NaHSO₃ (3:1 ratio; i.e., 0.54 mmol/kg and 0.18 mmol/kg body weight) orally 1 h after colitis induction followed by the administration of the same solution after each 12 h for 72 h. TNBS administration resulted in increased oxidative stress, NF-ĸ B and inflammasome activation, ER stress and autophagy. Moreover, TNBS administration also resulted in activation of p53 and apoptosis. SO₂ reversed all these alterations and ameliorated colitis in rats. Administration of an inhibitor of endogenous SO₂ production along with TNBS exacerbated colitis. Results suggest that down-regulation of SO₂ / glutamate oxaloacetate transaminase pathway is involved in IBD. The protective role of SO₂ in colitis is attributed to its anti-inflammatory and anti-oxidant nature. Down-regulation of SO₂/glutamate oxaloacetate transaminase pathway is involved in IBD. Since SO₂ is not toxic at low concentration and endogenously produced, it may be used with prescribed drugs for synergistic effect after intensive research. Our result demonstrated the therapeutic role of SO₂ in colitis for the first time.

Final Report on the Safety Assessment of Sodium Sulfite, Potassium Sulfite, Ammonium Sulfite, Sodium Bisulfite, Ammonium Bisulfite, Sodium Metabisulfite and Potassium Metabisulfite

Sodium Sulfite, Ammonium Sulfite, Sodium Bisulfite, Potassium Bisulfite, Ammonium Bisulfite, Sodium Metabisulfite, and Potassium Metabisulfite are inorganic salts that function as reducing agents in cosmetic formulations. All except Sodium Metabisulfite also function as hair-waving/straightening agents. In addition, Sodium Sulfite, Potassium Sulfite, Sodium Bisulfite, and Sodium Metabisulfite function as antioxidants. Although Ammonium Sulfite is not in current use, the others are widely used in hair care products. Sulfites that enter mammals via ingestion, inhalation, or injection are metabolized by sulfite oxidase to sulfate. In oral-dose animal toxicity studies, hyperplastic changes in the gastric mucosa were the most common findings at high doses. Ammonium Sulfite aerosol had an acute LC50 of >400 mg/m3 in guinea pigs. A single exposure to low concentrations of a Sodium Sulfite fine aerosol produced dose-related changes in the lung capacity parameters of guinea pigs. A 3-day exposure of rats to a Sodium Sulfite fine aerosol produced mild pulmonary edema and irritation of the tracheal epithelium. Severe epithelial changes were observed in dogs exposed for 290 days to 1 mg/m3 of a Sodium Metabisulfite fine aerosol. These fine aerosols contained fine respirable particle sizes that are not found in cosmetic aerosols or pump sprays. None of the cosmetic product types, however, in which these ingredients are used are aerosolized. Sodium Bisulfite (tested at 38%) and Sodium Metabisulfite (undiluted) were not irritants to rabbits following occlusive exposures. Sodium Metabisulfite (tested at 50%) was irritating to guinea pigs following repeated exposure. In rats, Sodium Sulfite heptahydrate at large doses (up to 3.3 g/kg) produced fetal toxicity but not teratogenicity. Sodium Bisulfite, Sodium Metabisulfite, and Potassium Metabisulfite were not teratogenic for mice, rats, hamsters, or rabbits at doses up to 160 mg/kg. Generally, Sodium Sulfite, Sodium Metabisulfite, and Potassium Metabisulfite were negative in mutagenicity studies. Sodium Bisulfite produced both positive and negative results. Clinical oral and ocular-exposure studies reported no adverse effects. Sodium Sulfite was not irritating or sensitizing in clinical tests. These ingredients, however, may produce positive reactions in dermatologic patients under patch test. In evaluating the positive genotoxicity data found with Sodium Bisulfite, the equilibrium chemistry of sulfurous acid, sulfur dioxide, bisulfite, sulfite, and metabisulfite was considered. This information, however, suggests that some bisulfite may have been present in genotoxicity tests involving the other ingredients and vice versa. On that basis, the genotoxicity data did not give a clear, consistent picture. In cosmetics, however, the bisulfite form is used at very low concentrations (0.03% to 0.7%) in most products except wave sets. In wave sets, the pH ranges from 8 to 9 where the sulfite form would predominate. Skin penetration would be low due to the highly charged nature of these particles and any sulfite that did penetrate would be converted to sulfate by the enzyme sulfate oxidase. As used in cosmetics, therefore, these ingredients would not present a genotoxicity risk. The Cosmetic Ingredient Review Expert Panel concluded that Sodium Sulfite, Potassium Sulfite, Ammonium Sulfite, Sodium Bisulfite, Ammonium Bisulfite, Sodium Metabisulfite, and Potassium Metabisulfite are safe as used in cosmetic formulations.

Gastric mucosal irritation following oral exposure to sodium metabisulphite: A reproducible effect?

Sulphiting agents, such as sodium metabisulphite (SM), are used in food as bleaching agents and to prevent browning reactions. A 1972 repeat dose study in rats found that dietary sulphites caused irritation of the stomach with inflammation, hyperplasia and bleeding. We conducted a 7-day dietary study in rats to confirm that stomach lesions were the most sensitive toxicological endpoint. Rat feed was prepared daily with 0%, 0.25%, 0.5%, 1% or 4% (w/w) SM. Parameters included clinical signs, feed and water intake, bodyweight gain, haematology, serum protein chemistry, necropsy findings and gastrointestinal histopathology. There were no treatment-related clinical signs or gastrointestinal lesions. Mean bodyweight gain was markedly decreased in the 4% (w/w) SM group although feed consumption was marginally depressed. Slightly lower mean values for RBC, Hb, Hct, total WBC and lymphocyte count were observed in the 4% SM group with no evidence of compensatory haematopoiesis. The gastric lesions in rats observed in a 1972 study of dietary SM for 10-56 days could not be replicated. These findings create uncertainty around the most relevant toxicological endpoint to establish a suitable health based guidance value, which can only be overcome if a robust long-term dietary study is undertaken.

The effect of sulfite and chronic restraint stress on brain lipid peroxidation and anti-oxidant enzyme activities

Sulfites are used as anti-microbial and anti-oxidant agents in a variety of drugs, and function as a preservative in many food preparations. In addition to these effects, sulfites oxidize to sulfite radicals initiating lipid peroxidation. The objective of our study was to investigate the effect of restraint stress and sulfite on brain lipid peroxidation and anti-oxidant enzyme activities. Forty male Wistar rats, aged three months, were randomized to one of the following groups: control, restraint stress, sulfite-treated and restraint stress-/sulfite-treated. Chronic restraint stress was applied for 21 days (1 h/day) and sodium metabisulfite (520 mg/kg per day) was given by gavage for the same period. Lipid peroxidation was measured using the thiobarbituric acid (TBA) fluorometric assay. TBA-reactive substances (TBARS) were found increased in all treatment groups when compared to the control group. Spectrophotometric measurement of copper/zinc superoxide dismutase (Cu/Zn SOD) and catalase (CAT) revealed decreased enzyme activities in rats exposed to restraint stress compared to control and sulfite-treated rats. GSH-Px activities were significantly decreased in the restraint stress and sulfite-treated rats compared with the control rats. GSH-Px activity measured in restraint stress-/sulfite-treated rats was significantly lower than in the other groups. The presented data confirms the pro-oxidant activity of restraint stress and establishes that decreased anti-oxidant enzyme activities in restraint stress-treated rats enhances brain lipid peroxidation caused via the ingestion of sulfites.

The molecular mechanisms of sodium metabisulfite on the expression of K ATP and L-Ca2+ channels in rat hearts

Sodium metabisulfite (SMB) is used as an antioxidant and antimicrobial agent in a variety of drugs and foods. However, there are few reported studies about its side effects. This study is to investigate the SMB effects on the expression of ATP-sensitive K(+) (KATP) and L-type calcium (L-Ca(2+)) channels in rat hearts. The results show that the mRNA and protein levels of the KATP channel subunits Kir6.2 and SUR2A were increased by SMB; on the contrary, SMB at 520 mg/kg significantly decreased the expression of the L-Ca(2+) channel subunits Cav1.2 and Cav1.3. This suggests that SMB can activate the expression of KATP channel by increasing the mRNA and protein levels of Kir6.2 and SUR2A, while it inhibits the expression of L-Ca(2+) channels by decreasing the mRNA and protein levels of Cav1.2 and Cav1.3 in rat hearts. Therefore, the molecular mechanism of the SMB effect on rat hearts might be related to the increased expression of KATP channels and the decreased expression of L-Ca(2+) channels.

Effects of sodium metabisulfite on the expression of BK(Ca), K(ATP), and L-Ca(2+) channels in rat aortas in vivo and in vitro

Sodium metabisulfite (SMB) is most commonly used as the preservative in many food preparations and drugs. So far, few studies about its negative effects were reported. The purpose of this study was to investigate the effect of SMB on the expression of big-conductance Ca(2+)-activated K(+) (BKCa), ATP-sensitive K(+) (KATP), and L-type calcium (L-Ca(2+)) channels in rat aorta in vivo and in vitro. The results showed that the mRNA and protein levels of the BKCa channel subunits α and β1 of aorta in rats were increased by SMB in vivo and in vitro. Similarly, the expression of the KATP channel subunits Kir6.1, Kir6.2, and SUR2B were increased by SMB. However, SMB at the highest concentration significantly decreased the expression of the L-Ca(2+) channel subunits Cav1.2 and Cav1.3. These results suggest that SMB can activate BKCa and KATP channels by increasing the expression of α, β1, and Kir6.1, Kir6.2, SUR2B respectively, while also inhibit L-Ca(2+) channels by decreasing the expression of Cav1.2 and Cav1.3 of aorta in rats. The molecular mechanism of SMB-induced vasorelaxant effect might be related to the expression changes of BKCa, KATP, and L-Ca(2+) channels subunits. Further work is needed to determine the relative contribution of each channel in SMB-mediated vasorelaxant effect.

Ghrelin inhibits sodium metabisulfite induced oxidative stress and apoptosis in rat gastric mucosa

This study aimed to investigate the effect of ghrelin administration on sulfite induced oxidative and apoptotic changes in rat gastric mucosa. Forty male albino Wistar rats were randomized into control (C), sodium metabisulfite (Na2S2O5) treated (S), ghrelin treated (G) and, Na2S2O5+ghrelin treated (SG) groups. Sodium metabisulfite (100 mg/kg/day) was given by gastric gavage and, ghrelin (20 μg/kg/day) was given intraperitoneally for 5 weeks. Plasma-S-sulfonate level was increased in S and SG groups. Na2S2O5 administration significantly elevated total oxidant status (TOS) levels while depleting total antioxidant status (TAS) levels in gastric mucosa. Ghrelin significantly decreased gastric TOS levels in the SG group compared with the S group. Additionally, TAS levels were found to be higher in SG group in reference to S group. Na2S2O5 administration also markedly increased the number of apoptotic cells, cleaved caspase-3 and PAR expression (PARP activity indicator) and, decreased Ki67 expression (cell proliferation index) in gastric mucosal cells. Ghrelin treatment decreased the number apoptotic cells, cytochrome C release, PAR and, caspase-3 expressions while increasing Ki67 expression in gastric mucosa exposed to Na2S2O5. In conclusion, we suggest that ghrelin treatment might ameliorate ingested-Na2S2O5 induced gastric mucosal injury stemming from apoptosis and oxidative stress in rats.

Sodium metabisulfite induces lipid peroxidation and apoptosis in rat gastric tissue

Sodium metabisulfite (Na 2S2O5) is used as an antioxidant and antimicrobial agent in a variety of drugs and functions as a preservative in many food preparations. This study was performed to elucidate the dose-dependent effects of sodium metabisulfite ingestion on rat gastric tissue apoptotic changes and lipid peroxidation. Forty male wistar rats, aged 3 months were used. They were randomly divided into four groups: control (C), the group treated with Na2S2O5 (10 mg/kg; S1), the group treated with Na2S2O5 (100 mg/kg; S2), the group treated with Na2S2O5 (260 mg/kg; S3). Na 2S2O5 was given by intragastric intubation for 35 days. In the S2 and S3 groups, malondialdehyde (MDA) levels increased markedly when compared with the control group. High doses of sulfite administration elevated number of apoptotic cells both in mucosa and submucosa layers of stomach in parallel with increased MDA levels. These results suggest that sodium metabisulfite increased lipid peroxidation and thus number of apoptotic cells on gastric tissue in dose-dependent manner.

The effect of chronic restraint stress and sulfite on visual evoked potentials (VEPs): Relation to lipid peroxidation

Stress and sulfite can stimulate numerous pathways leading to an increased production of free radicals which generate a peroxidation cascade producing lipid peroxidation, protein oxidation, DNA damage and cell death, and contribute to the occurrence of pathologic conditions. The purpose of our study was to investigate the effects of stress and sulfite on visual evoked potentials (VEPs) and to examine the relationship between lipid peroxidation and VEP changes. Forty male wistar rats, aged three months were used. They were equally divided into four groups: control (C), the group exposed to restraint stress (R), the group treated with sulfite (S) and the group exposed to stress and treated with sulfite (RS). Chronic restraint stress was applied for 21 days (1h/day) and sodium metabisulfite (520 mg/kg/day) was given by gavage for the same period. All latencies of VEP components were prolonged in the R, S and RS groups with respect to the C group. Brain and retina TBARS levels were found to be increased in those groups compared to the C group. Our results strongly suggest that the latency prolongations of all VEP components may have resulted from the enhancement of lipid peroxidation. Correlation analysis between brain and retina TBARS levels and VEP latencies also support this conclusion. Our data in regard to latency prolongations of all VEP components in the stress group exposed to sulfite, reflected an additive effect of sulfite toxicity on VEP components. Therefore it could be suggested that chronic exposure to stress and sulfite together is associated with a considerable health risk.

The prooxidant effect of sodium metabisulfite in rat liver and kidney

Sodium metabisulfite (Na2S2O5) is used as an antioxidant and antimicrobial agent in a variety of drugs and functions as a preservative in many food preparations. In addition to their antioxidant activity, sulfites oxidize to sulfite radicals (SO3-) initiating lipid peroxidation. This study was performed to elucidate the effect of subchronic Na2S2O5 (520 mg/kg/day) ingestion on hepatic and renal antioxidant enzyme activities and lipid peroxidation in albino rats. The antioxidant effect of l-carnitine was also tested in rats treated with Na2S2O5. Plasma uric acid levels were monitored in all rats included in the study. Malondialdehyde (MDA) levels significantly increased in Na2S2O5 treated rats vs. controls, with kidney values of 2.21+/-0.21 vs. 1.22+/-0.35 and liver values of 79.85+/-19.5 vs. 31.36+/-5.0 nmol/mg protein, respectively. Selenium-glutathione peroxidase (GPx) activity was significantly increased in Na2S2O5 treated rats vs. controls, with kidney values of 38.22+/-2.21 vs. 8.09+/-0.76 and liver values of 31.11+/-6.37 vs. 11.70+/-1.02 U/g protein, respectively. Sodium metabisulfite treatment increased plasma uric acid levels in rats that were included in the study. No protective effect of l-carnitine was observed against lipid peroxidation in both liver and kidneys of rats treated with Na2S2O5. The presented data confirm the prooxidant activity of sulfites and suggest that increased GPx activity and plasma uric acid levels may partially reduce the observed renal and hepatocellular oxidative damage caused via the ingestion of sulfites.

Absence of adverse effects of sodium metabisulphite in manufactured biscuits: results of subacute (28-days) and subchronic (85-days) feeding studies in rats

Sulphites are extensively used in the food and drinks industry. Their toxicity has been previously evaluated by addition to the diet or drinking water of laboratory animals. Because interactions between sulphites and food constituents occur, the present work was conducted to determine the subacute and subchronic toxicity of sulphite-bound compounds in a finished product: manufactured biscuits. The studies were performed on Sprague Dawley, rats for 28 and 85 days of dietary exposure. Diets were prepared from sulphited or untreated (controls) biscuits with the addition of sugar, protein, vitamins and minerals according to the nutritional requirements of the animals. Groups of 10 male and 10 female rats were administered diets containing sulphited biscuits at levels of 0, 10, 35 and 75%, corresponding to 10-15, 35-45, 150-170 and 310-340 mg SO2/kg diet. In both studies, no death or clinical abnormalities were reported. Growth rate, food consumption and food conversion efficiency were not affected by treatment. No dose-related changes were observed for haematology, clinical chemistry, ocular examination, renal-function, urinalysis, organ weights or gross and microscopic examinations. The liver concentrations of vitamins A, B1, C and E were not significantly changed except for an increase in vitamin E in high-dose males after 28 days' exposure. Based on these data, the no-observed-adverse-effect level (NOAEL) of sulphites in baked biscuits was judged to be 310 mg SO2/kg diet or 25 mg/kg body weight/day.

Toxicology of sulphiting agents. I: Animal studies

Oral toxicity studies of sulphite in animals are briefly reviewed. On the basis of a chronic toxicity/carcinogenicity study of sodium metabisulphite in rats JECFA established an ADI of 0.7 mg SO2/kg using a safety factor of 100. The effects of sodium metabisulphite (1% Na2S2O5) on the composition of semi-purified rat diets during storage for at least three months have been studied. Under these conditions sulphite induced rancid off-flavours in diets containing unsaturated fats. The feeding of such stored sulphited-diets to rats resulted in growth retardation and diminished food efficiency. The extractability of the lipids from these diets was markedly reduced. Extraction with hexane, followed by ethanol extraction did not remove the toxic factor(s). It was suggested that sulphite in stored semi-purified diets may react with unsaturated fats leading to the formation of polymers of unsaturated fatty acids and/or other toxic substances. It is recommended that special attention is paid to the fatty acid composition of sulphited foods to be stored.