Antiarthritic activity of OA-DHZ; a gastroprotective NF-κB/MAPK/COX inhibitor

Arthritis, a primary autoimmune disorder having a global incidence of 2.03% person/year, is presently being treated by many commercially available drugs that treat symptomatically or improve the disease's clinical state; however, all the therapies pose varying amount of side effects. Therefore, it has become a fundamental need to search for therapeutics that offer better efficacy and safety profile, and the natural or nature-derived products are known for their outstanding performance in this arena. OA-DHZ, known to possess anti-inflammatory and analgesic properties, when explored for its efficacy against arthritis in adjuvant-induced arthritis (AIA) model, was found to inhibit paw edema by 34% and TNF-α, IL-6, and IL-1β by 67%, 39%, and 45% respectively when compared to diseased control. It was also able to reduce the inflamed spleen size by 45% and successfully normalized biochemical and hematological changes that followed arthritis. In vitro studies revealed that the underlying mechanism for inhibiting arthritis progression might be due to NF-κB /MAPK pathway modulation. OA-DHZ also showed selective inhibition of COX-2 in vitro while showing gastroprotective effects when evaluated for ulcerogenic and antiulcer potential in vivo. In contrast to the results obtained from in vivo experimentation, there is a disparity in the pharmacokinetic profile of OA-DHZ, where it showed low oral exposure and high clearance rate. OA-DHZ being antiarthritic acting via NF-κB /MAPK/ COX inhibition while showing gastroprotective effects, can be a suitable candidate to be in the drug pipeline and further exploration.

Anti-Inflammatory Potential of 1-Nitro-2-Phenylethylene

Inflammation is a reaction of the host to infectious or sterile stimuli and has the physiological purpose of restoring tissue homeostasis. However, uncontrolled or unresolved inflammation can lead to tissue damage, giving rise to a plethora of chronic inflammatory diseases, including metabolic syndrome and autoimmunity pathologies with eventual loss of organ function. Beta-nitrostyrene and its derivatives are known to have several biological activities, including anti-edema, vasorelaxant, antiplatelet, anti-inflammatory, and anticancer. However, few studies have been carried out regarding the anti-inflammatory effects of this class of compounds. Thereby, the aim of this study was to evaluate the anti-inflammatory activity of 1-nitro-2-phenylethene (NPe) using in vitro and in vivo assays. Firstly, the potential anti-inflammatory activity of NPe was evaluated by measuring TNF-α produced by human macrophages stimulated with lipopolysaccharide (LPS). NPe at non-toxic doses opposed the inflammatory effects induced by LPS stimulation, namely production of the inflammatory cytokine TNF-α and activation of NF-κB and ERK pathways (evaluated by phosphorylation of inhibitor of kappa B-alpha [IκB-α] and extracellular signal-regulated kinase 1/2 [ERK1/2], respectively). In a well-established model of acute pleurisy, pretreatment of LPS-challenged mice with NPe reduced neutrophil accumulation in the pleural cavity. This anti-inflammatory effect was associated with reduced activation of NF-κB and ERK1/2 pathways in NPe treated mice as compared to untreated animals. Notably, NPe was as effective as dexamethasone in both, reducing neutrophil accumulation and inhibiting ERK1/2 and IκB-α phosphorylation. Taken together, the results suggest a potential anti-inflammatory activity for NPe via inhibition of ERK1/2 and NF-κB pathways on leukocytes.

Toxicology and carcinogenesis studies of alpha-methylstyrene (Cas No. 98-83-9) in F344/N rats and B6C3F1 mice (inhalation studies)

alpha-Methylstyrene is used in the production of acrylonitrile-butadiene-styrene resins and copolymers, which improve the impact and heat-resistant properties of polymers, specialty grades of plastics, rubber, and protective coatings. alpha-Methylstyrene also moderates polymerization rates and improves product clarity in coatings and resins. Low molecular weight liquid polymers are used as plasticizers in paints, waxes, adhesives, and plastics. alpha-Methylstyrene was nominated by the U.S. Environmental Protection Agency for toxicologic evaluation and genotoxicity studies based on its high production volume and limited information available on its toxicity. Male and female F344/N rats and B6C3F1 mice were exposed to alpha-methylstyrene (99.5% pure) by inhalation for 3 months or 2 years. Inhalation studies were conducted because the primary route of human exposure is via inhalation. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed by whole-body inhalation to alpha-methylstyrene at concentrations of 0, 75, 150, 300, 600, or 1,000 ppm for 6 hours per day, 5 days per week for 14 weeks. Additional clinical pathology groups of 10 male and 10 female rats were exposed to the same concentrations for 23 days. All rats survived to the end of the study, and mean body weights of all exposed groups were similar to those of the chamber controls. Kidney weights were significantly increased in 1,000 ppm males and 600 and 1,000 ppm females. Statistically significant increases in liver weights occurred in 150 ppm or greater males and 600 and 1,000 ppm females. The incidences of renal hyaline droplet accumulation were similar between exposed groups and chamber control groups, but the severity of hyaline droplet accumulation in 600 and 1,000 ppm males was greater than in chamber controls. Consistent with the hyaline droplet accumulation, an exposure-related increase in alpha2μ-globulin was detected in the kidneys of males exposed to alpha-methylstyrene. Morphologic changes were not detected in the liver. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed by whole-body inhalation to alpha-methylstyrene at concentrations of 0, 75, 150, 300, 600, or 1,000 ppm for 6 hours per day, 5 days per week for 14 weeks. Two female mice in the 1,000 ppm group died before exposure on day 3. Final mean body weights of 600 and 1,000 ppm males and 75, 300, and 1,000 ppm females were significantly less than those of the chamber controls; final mean body weight gains of mice exposed to 300 ppm or greater were also significantly less. Moderate to severe sedation (males only) and ataxia were observed in 1,000 ppm mice. The absolute liver weights of 600 and 1,000 ppm females and the relative liver weights of 300, 600, and 1,000 ppm males and females were significantly increased. The estrous cycle lengths of 600 and 1,000 ppm female mice were significantly longer than that of the chamber controls. Minimal to mild centrilobular hypertrophy was present in the livers of male and female mice exposed to 600 or 1,000 ppm alpha-methylstyrene. The incidences of exposure-related nasal lesions, including atrophy and hyperplasia of Bowman's glands and atrophy and metaplasia of the olfactory epithelium, were significantly increased in all exposed groups of males and females. The incidences of hyaline degeneration, characterized by the accumulation of eosinophilic globules in the cytoplasm of the respiratory epithelium, were significantly increased in females exposed to 150 ppm or greater. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed by whole body inhalation to alpha-methylstyrene at concentrations of 0, 100, 300, or 1,000 ppm for 6 hours per day, 5 days per week, except holidays, for 105 weeks. Survival rates of exposed male and female rats were similar to those of the chamber controls. The mean body weights of 1,000 ppm males and females were less than those of the chamber control groups during year 2 of the study. Two 1,000 ppm males and one 300 ppm male had renal tubule carcinomas, and one 300 ppm male had a renal tubule adenoma. Because of the neoplasms observed in 300 and 1,000 ppm males at the end of the 2-year study and the finding of alpha2μ-globulin accumulation in the kidneys at 3 months, which is often associated with kidney neoplasms, additional step sections of kidney were prepared; additional males with focal hyperplasia or adenoma were identified. The incidences of renal tubule adenoma and carcinoma (combined) in the 1,000 ppm males were significantly greater than those in the chamber controls when the single and step sections were combined. The incidence of mineralization of the renal papilla was significantly increased in 1,000 ppm males. The incidence of mononuclear cell leukemia in 1,000 ppm males was significantly increased compared to the chamber controls. In the nose, the incidences of basal cell hyperplasia were significantly increased in all exposed groups of males and females, and the incidences of degeneration of the olfactory epithelium were increased in 1,000 ppm males and females and 300 ppm females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed by whole body inhalation to alpha-methylstyrene at concentrations of 0, 100, 300, or 600 ppm for 6 hours per day, 5 days per week, except holidays, for 105 weeks. Survival of all exposed male and female mice was similar to that of the chamber control groups. Mean body weights of 600 ppm males were less than those of the chamber control group throughout the study, and those of 600 ppm females were less after week 13. The mean body weights of 300 ppm males and females were less than those of the chamber controls during much of the study, but these groups recovered by the end of the study. The incidences of hepatocellular adenoma or carcinoma (combined) were significantly increased in the 100 and 600 ppm males and in all exposed groups of females. The incidences of hepatocellular adenoma were significantly increased in all exposed groups of females, and the incidences in all exposed groups of males and females exceeded the historical range for chamber controls. The incidences of hepatocellular carcinoma and eosinophilic foci of the liver were significantly increased in 600 ppm females. The incidences of olfactory epithelial metaplasia and hyperplasia of the glands overlying the olfactory epithelium were significantly increased in all exposed groups of males and females. In addition, atrophy of the olfactory epithelium was significantly increased in 300 and 600 ppm males. The incidence and severity of nephropathy were increased in 600 ppm females compared to chamber controls. Epithelial hyperplasia of the forestomach also was present in male mice.

GENETIC TOXICOLOGY

alpha-Methylstyrene was not mutagenic in four strains of Salmonella typhimurium, with or without rat or hamster liver metabolic activation enzymes (S9). alpha-Methylstyrene did not induce chromosomal aberrations in cultured Chinese hamster ovary cells, with or without S9 activation, but did significantly increase the frequency of sister chromatid exchanges in cultures exposed in the presence of S9. In vivo, no significant increases in the frequencies of micronucleated erythrocytes were seen in blood samples of male mice obtained at the conclusion of the 3-month study. However, in female mice from the 3-month study, a significant increase in micronucleated erythrocytes was observed in the 1,000 ppm group.

CONCLUSIONS

Under the conditions of this 2-year inhalation study, there was some evidence of carcinogenic activity of alpha-methylstyrene in male F344/N rats based on increased incidences of renal tubule adenomas and carcinomas (combined). The increased incidence of mononuclear cell leukemia in 1,000 ppm male F344/N rats may have been related to alpha-methylstyrene exposure. There was no evidence of carcinogenic activity of alpha-methylstyrene in female F344/N rats exposed to 100, 300, or 1,000 ppm. There was equivocal evidence of carcinogenic activity of alpha-methylstyrene in male B6C3F1 mice based on marginally increased incidences of hepatocellular adenoma or carcinoma (combined). There was clear evidence of carcinogenic activity of alpha-methylstyrene in female B6C3F1 mice based on increased incidences of hepatocellular adenomas and carcinomas. Exposure of rats to alpha-methylstyrene resulted in kidney toxicity, which in males exhibited some features of alpha2μ-globulin nephropathy. Exposure to alpha-methylstyrene resulted in nonneoplastic lesions of the nose in male and female rats and mice and of the liver and kidney in female mice.

Comparison of the rapid pro-apoptotic effect of trans-ß-nitrostyrenes with delayed apoptosis induced by the standard agent 5-fluorouracil in colon cancer cells

Trans-beta-nitrostyrene (TBNS) has been reported to be a potent inhibitor of protein phosphatases PTB1 and PP2A and to display a pro-apoptotic effect even in multidrug resistant tumour cells. Here we compared the anti-tumour potential of TBNS with 5-fluorouracil (5-FU) as the standard chemotherapeutic agent for colorectal cancer in LoVo cells. Resistance to 5-FU based therapy might be a consequence of 5-FU's delayed effect requiring long-term effective concentrations in the tumour tissue. Thus, alternatives like platin containing drugs with a more rapid effect have been introduced recently. Compared to 5-FU TBNS displayed a faster cytotoxic and pro-apoptotic effect. A 50% decrease in viability was observed already after 8 h with TBNS while 5-FU displayed no significant effect before 48 h. DNA fragmentation and caspase-3 assays confirmed the more rapid apoptotic effect of TBNS. Since apoptosis affects individual cells these results about a rapidly induced apoptosis were further studied on a single cell level in microscopic assays of caspase-3 and caspase-8 activation. Adducts of trans-beta-nitrostyrene displayed an anti-tumour effect comparable to TBNS which suggests the possibility of creating adducts with optimised tissue targeting. Finally, the calculation of a drug combination index displayed a synergistic effect for the combination of TBNS and 5-FU in Lovo as well as in HT-29 and HCT116 colon cancer cells.

[A case of diffuse invasive hepatocellular carcinoma associated with thrombosis of the main trunk of the portal vein in which hepatic transcatheter arterial chemoembolization concomitant to the use of degradable starch microspheres (DSM-TACE) was very effective]

The case reported here was a 80-year-old male who was presented with a diffuse type of hepatocellular carcinoma accompanied by thrombosis of the main trunk of the portal vein. The primary focus and portal vein thrombosis improved considerably following repeated transcatheter arterial chemoembolization using DSM (DSM-TACE). DSM-TACE was suggested to have the potential for becoming a new treatment method for advanced hepatocellular carcinoma, for which conventional transcatheter arterial embolization (TAE) using Lipiodol and so forth is contraindicated tue to thrombosis of the main trunk of the portal vein.

Synthesis, spectra, delivery and potentiometric responses of new styryl dyes with extended spectral ranges

Styryl dyes have been among the most widely used probes for mapping membrane potential changes in excitable cells. However, their utility has been somewhat limited because their excitation wavelengths have been restricted to the 450-550 nm range. Longer wavelength probes can minimize interference from endogenous chromophores and, because of decreased light scattering, improve recording from deep within tissue. In this paper we report on our efforts to develop new potentiometric styryl dyes that have excitation wavelengths ranging above 700 nm and emission spectra out to 900 nm. We have prepared and characterized dyes based on 47 variants of the styryl chromophores. Voltage-dependent spectral changes have been recorded for these dyes in a model lipid bilayer and from lobster nerves. The voltage sensitivities of the fluorescence of many of these new potentiometric indicators are as good as those of the widely used ANEP series of probes. In addition, because some of the dyes are often poorly water soluble, we have developed cyclodextrin complexes of the dyes to serve as efficient delivery vehicles. These dyes promise to enable new experimental paradigms for in vivo imaging of membrane potential.

RISUG (reversible inhibition of sperm under guidance)--an antimicrobial as male vas deferens implant for HIV free semen

HIV transmission from the male to the female is a major health problem. A hypothesis proposing an intra vas deferens implant of an antimicrobial compound to prevent the infection spread is presented. Mechanisms of action for the inhibition could include inactivating HIV in sperms passing through the vas deferens; drug release from the implant to destroy HIV entering into semen from genital structures distal to the vas deferens; and sperm acrosome released hyaluronidase mediated reabsorption of HIV. A subcomponent of the implant flowing along sperm pathway may have a role in reducing the entry of HIV from a positive female into penile tissue. A new drug RISUG (reversible inhibition of sperm under guidance) presently undergoing clinical trials for its contraceptive effect in the male (because it disrupts the sperm acrosome by an electrical charge and pH lowering effects) has also antimicrobial action. The drug being a combination of styrene maleic anhydride (SMA) and dimethyl sulfoxide (DMSO) on being injected into the lumen of the vas deferens produces styrene maleic acid thereby lowering pH; induces electrochemical action leading to a stable electrical charge generation; releases mandelic acid; and induces acrosome reaction in sperms with consequent release of hyaluronidase and sperm inactivation. Moreover, one time administration into the lumen of the vas gives long term action. All these phenomena very well match with the needs for HIV clearance of semen and hence RISUG is here proposed as a possible candidate material for the HIV inhibiting vas deferens implant when delivered in below contraceptive threshold dosage. For experimental validation, after obtaining data on the semen HIV load under control conditions in the HIV positive males inducted into the study, 30 mg of SMA in 120 microl of DMSO (contraceptive dose being 60 mg SMA+120 microl DMSO) is to be injected into vasa deferens bilaterally. Thereafter at intervals of one month the viral load needs to be determined in semen obtained either by masturbation or in lubricant free condom at intercourse - the method of collection remaining the same throughout for a particular subject. A significant reduction in the semen viral load following RISUG administration will validate the hypothesis. Speculated reduced female to male HIV transmission is more difficult to test. Nonspecific indications will come from a population study of the incidence of RISUG treated men becoming HIV positive as compared to that in the general population.

The chemotherapy of rodent malaria. LX. The importance of formulation in evaluating the blood schizontocidal activity of some endoperoxide antimalarials

The activities of artemisinin (QHS) and a number of its semi-synthetic analogues, as well as Fenozan B07 (B07), a synthetic 1,2,4-trioxane, and arteflene (ATF), a synthetic surrogate of yingzhaosu, were compared in mice infected with drug-sensitive Plasmodium berghei or chloroquine-resistant P. yoelii ssp. NS. The studies were stimulated by the observation that B07, in certain aqueous preparations, appears to be equipotent by the subcutaneous (sc) or oral (po) routes in the rodent model but not in a simian model. In the rodent model, B07 was found to undergo rapid alteration (with a half-life of <24h) in an aqueous stock solution prepared using dimethyl sulphoxide (DMSO) to pre-dissolve the drug. Therefore, for all later experiments with aqueous preparations, the test material was newly formulated each day. In a carboxymethylcellulose formulation used as a 'standard suspending vehicle' (SSV), B07 and dihydroartemisinin (DIHYD) were found to be, respectively, one sixth and one 10th as active po as when the drugs were pre-dissolved in DMSO and then diluted with water. ATF in DMSO given po was less than one 20th as active as when used sc in the rodent model, and this drug in SSV was almost inactive po. The relatively low oral activity of these three compounds (especially DIHYD and ATF) may be attributable to extensive first-pass metabolism in the mouse. Oral beta-artemether (AM) and beta-arteether (AE) were highly active when used in SSV. ATF has been found to have low activity in simian models and clinical trials because of its poor absolute bio-availability. In in-vivo studies of the blood schizontocidal action of anti-malarials, in rodent malaria models, the data collected on the structure-activity relationships (SAR) of the drugs must be viewed critically when selecting specific compounds from a chemical series for further development. A study of the influence of drug formulation on the activity of other, novel antimalarials is crucial to the evaluation of the drugs, and merits high priority.

Effect of a new injectable male contraceptive on the seminal plasma amino acids studied by proton NMR spectroscopy

Effect of RISUG, a newly developed male contraceptive, on various amino acids of seminal plasma ejaculates was studied by proton magnetic resonance spectroscopy at 400 MHz. Levels of amino acids were compared with the seminal plasma of obstructive azoospermia and controls. Glutamic acid, glutamine, and arginine were found to be high in concentration in human seminal plasma. The concentration of aromatic amino acids such as tyrosine, histidine, and phenylalanine in RISUG-injected subjects showed no significant difference compared to controls (p > 0.1); however, there was a statistically significant decrease in the concentration of these amino acids in obstructive azoospermia. The concentration of some prominent amino acids that showed overlapping resonances, such as isoleucine+leucine+valine (p < 0.01), alanine+isoleucine+lysine (p < 0.01), arginine+lysine+leucine (p < 0.01), and glutamic acid+glutamine (p < 0.01), showed a statistically significant decrease in RISUG-injected subjects compared to controls. Overlap of these amino acid resonances were noticed even at 600 MHz. In general, the total amino acids concentration in RISUG-injected subjects was found to be higher than in azoospermic subjects, confirming the occurrence of 'partial' obstructive azoospermia in subjects injected with this contraceptive.

A proton NMR study of the effect of a new intravasal injectable male contraceptive RISUG on seminal plasma metabolites

Nuclear magnetic resonance (NMR) spectroscopy was used to quantify citrate, glucose, lactate, glycerophosphorylcholine and choline in seminal plasma from subjects injected with a new male contraceptive RISUG, a copolymer of styrene maleic anhydride dissolved in dimethyl sulphoxide, and in seminal plasma from normal ejaculates. No significant difference in the concentration of citrate was observed between the groups, indicating that the prostate is not affected by the contraceptive. The concentrations of glucose, lactate, glycerophosphorylcholine and choline were significantly lower (P < 0.01) in subjects injected with RISUG compared with controls. In addition, metabolite ratios such as choline:citrate, citrate:lactate, choline:lactate and glycerophosphorylcholine:choline were calculated. Citrate:lactate and glycerophosphorylcholine:choline ratios were significantly lower in RISUG-injected subjects than in controls (P < 0.01), thereby indicating the occurrence of partial obstructive azoospermia. The most important finding of the present study was that the intervention of RISUG in the vas deferens even for a period as long as 8 years is absolutely safe and does not lead to prostatic diseases.

Ring test for the determination of N-terminal valine adducts of styrene 7,8-oxide with haemoglobin by the modified Edman degradation technique

A ring-test was organised between three laboratories using different versions of the modified Edman degradation technique for the gas chromatographic-mass spectrometric determination of N-terminal valine adducts of styrene 7,8-oxide. The analyses were performed on a sample of human haemoglobin reacted in vitro with styrene 7,8-oxide and on a set of five haemoglobin samples from mice dosed by i.p. injection of styrene. Strong correlations between the haemoglobin adduct determinations of the different laboratories were observed. However, covariance analysis revealed different slopes for the dose-response curves, indicating differences for the calibration of the reference globin or reference peptide.

Styrene-induced alterations in the respiratory tract of rats treated by inhalation or intraperitoneally

Although exposure to styrene occurs primarily via inhalation, the action of this agent on the respiratory tract has scarcely been investigated. This article describes morphological and biochemical changes occurring in the respiratory tract of rats after either inhalation of styrene vapors (300 ppm, 6 h/d, 5 d/wk, for 2 wk) or systemic (ip) treatment with 40 or 400 mg/kg styrene for 3 consecutive days. Electron microscopy analysis showed diffuse cell damage involving the tracheal, bronchiolar, and alveolar epithelium. In the tracheal epithelium, several cell types were affected. Ciliated cells presented vacuolation, detachment of cilia, blebbing of the apical cytoplasm, and compound cilia. Most secretory cells showed scant secretory granules and blebbings. Dense bodies and fibrillary inclusions were seen in intermediate and basal cells. Styrene also caused alterations of cytoplasmic components in type II pneumocytes and bronchiolar cells as well as thickness of the alveolar wall. These abnormalities were accompanied by depletion of glutathione (GSH) in the lung tissue. Pneumotoxic effects of systemic administration of styrene were dose dependent and tended to be more severe than those seen in the animals exposed for longer periods to styrene by inhalation. Metabolic activation of styrene and subsequent cell damage induced by the reactive metabolite styrene oxide may be involved in the sequence of events culminating in the toxic insult to the respiratory tract.

Effects of various pretreatments on the hepatotoxicity of inhaled styrene in the B6C3F1 mouse

1. The roles of cytochrome P450 monooxygenases (P450) and glutathione (GSH) in styrene hepatotoxicity were investigated in mice by pretreating with either phenobarbital (PB; P450 inducer), SKF 525A (P450 inhibitor), N-acetylcysteine (NAC; GSH precursor), or saline (vehicle control) prior to a 6-h exposure to either 500 ppm styrene on air. 2. Styrene caused hepatocellular degeneration or necrosis in all groups; these changes were more extensive and severe in mice pretreated with PB. Styrene significantly increased relative liver weights and serum ALT and SDH levels only in mice pretreated with PB. NAC did not prevent GSH depletion or hepatotoxicity. 3. In the fat of SKF 525A-pretreated mice a slight but statistically significant increase in styrene levels was observed, suggesting that metabolism was decreased; the SO/styrene ratio in the fat of PB-pretreated mice showed a slight, but statistically significant, increase indicating a slight increase in styrene metabolism. Neither SKF 525A nor PB caused changes in microsomal enzyme activity in vitro. 4. These results suggest that styrene may be activated by a pathway not totally dependent upon P450 enzyme activity, or more likely that PB and SKF 525A are not specific for the P450 enzymes involved in activation and detoxification of styrene.

Subchronic inhalation studies of styrene in CD rats and CD-1 mice

Groups of 10 male and 10 female Charles River (CRL) CD (Sprague-Dawley-derived) rats were exposed to styrene vapor at 0, 200, 500, 1000, or 1500 ppm 6 hr per day 5 days per week for 13 weeks. Styrene had no effect on survival, hematology, or clinical chemistry. Males at 1500 ppm weighed 10% less after 13 weeks and males and females at 1000 and 1500 ppm consumed more water than controls. Histopathologic changes were confined to the olfactory epithelium of the nasal mucosa. Groups of 20 male and 20 female CRL CD-1 and B6C3F1 mice were exposed to styrene vapor at 0, 15, 60, 250, or 500 ppm 6 hr per day 5 days per week for 2 weeks. Mortality was observed in both CD-1 and B6C3F1 mice exposed to 250 or 500 ppm; more female mice, but not males, died from exposure to 250 ppm than from 500 ppm. Groups of 10 male and 10 female CRL CD-1 mice were exposed to styrene vapors at 0, 50, 100, 150, or 200 ppm 6 hr per day 5 days per week for 13 weeks. Two females exposed to 200 ppm died during the first week. Liver toxicity was evident in the decedents and in some female survivors at 200 ppm. Changes were observed in the lungs of mice exposed to 100, 150, or 200 ppm and in the nasal passages of all treatment groups, those exposed to 50 ppm being less affected. Satellite groups of 15 male rats and 30 male mice were exposed as described above for 2, 5, or 13 weeks for measurement of cell proliferation (BrdU labeling). No increase in cell proliferation was found in liver of rats or mice or in cells of the bronchiolar or alveolar region of the lung of rats. No increase in labeling index of type II pneumocytes was seen in mouse lungs, while at 150 and 200 ppm, an increased labeling index of Clara cells was seen after 2 weeks and in occasional mice after 5 weeks. Large variations in the labeling index among animals emphasize the need for large group sizes. For nasal tract effects, a NOAEL was not found in CD-1 mice, but in CD rats, the NOAEL was 200 ppm. For other effects, the NOAEL was 500 ppm in rats and 50 ppm in mice.

Comparison of average estimated metabolic rates for styrene in previously exposed and unexposed groups with pharmacokinetic modelling

OBJECTIVE

To understand whether previous styrene exposure increases the human liver's ability to convert styrene into styrene oxide.

METHODS

The hypothesis was tested that the average linear metabolic rate constant kappa was the same in both exposed and unexposed groups, when the exposed group comprised people with a history of styrene exposure and the unexposed group had no exposure. In an experimental chamber, these two groups of subjects were exposed to a concentration of 80 ppm styrene for two hours. A three compartment pharmacokinetic model was used to define kappa. Based on large sample theory, the comparison of estimated mean values of kappa in the exposed and unexposed groups was shown to be equivalent to a comparison of the estimated mean values of the hepatic clearance X in the two groups. A method was developed to estimate X for each subject in both groups from the subject's height, weight, and estimated asymptotic styrene decay constant alpha. Here, alpha was estimated individually from observed blood concentrations over time when sufficient time had elapsed after the controlled exposure.

RESULTS

The proposed methodology of comparing the estimated mean values of kappa in exposed and unexposed groups reduced the number of specific physiological variables involved to three, all of which were estimable from data based on simple direct measurements. In contrast, other methods based on pharmacokinetic models usually involved many variables that were non-estimable on an individual basis. Consequently, statistical comparisons were impossible. These methods were applied to analyse previously published data on the time course of styrene concentrations in arterial blood of subjects in both exposed and unexposed groups. A Wilcoxon non-parametric rank sum test with the individually estimated X values was used, and no significant difference in the means of X in the two groups was found.

CONCLUSION

The linear metabolic rate constant kappa for humans is probably not altered by previous exposure to styrene. This result is in agreement with some experimental studies on animals. However, in the data analysis, it was noted that the number of subjects in each group was small (6-7) and that the styrene concentration data did not exactly reflect true behaviour of asymptotic decay. Further studies are still needed to draw more definitive conclusions.

Pneumotoxicity and hepatotoxicity of styrene and styrene oxide

The purpose of this study was to investigate the toxicity of styrene and styrene oxide in the lung in comparison to the toxicity in the liver. Pneumotoxicity caused by styrene or styrene oxide was measured by elevations in the release of gamma-glutamyltranspeptidase (GGT) and lactate dehydrogenase (LDH) into bronchoalveolar lavage fluid (BALF), while hepatotoxicity was measured by increases in serum sorbitol dehydrogenase (SDH) in non-Swiss Albino (Hsd:NSA) mice. Intraperitoneal administration of styrene at doses of 500-1000 mg/kg caused consistent dose-dependent increases in both sets of biomarkers with the hepatic effect appearing earlier than the pulmonary effect. Pyridine, phenobarbital, and beta-naphthoflavone, inducers of CYP2E1, CYP2B, and CYP1A, respectively, increased the toxicity of styrene. Pyridine and phenobarbital treatments increased mortality due to styrene. Styrene oxide exists in two enantiomeric forms: (R)- and (S)-styrene oxide, and the differential toxicities of the two enantiomers and racemic styrene oxide were compared. In all studies, (R)-styrene oxide caused greater toxicity than the (S) enantiomer, especially in the liver. Trichloropropene oxide, an epoxide hydrolase inhibitor, was used to inhibit styrene oxide detoxification and increased its hepatotoxicity, while buthionine sulfoxamine, a glutathione depletor, did not. These results demonstrated the greater role of epoxide hydrolase in styrene oxide detoxification.

Effects of ethanol administration on cerebral non-protein sulfhydryl content in rats exposed to styrene vapour

Glutathione (GSH) and other non-protein sulfhydryls (NPS) are known to protect cells from oxidative stress and from potentially toxic electrophiles formed by biotransformation of xenobiotics. This study examined the effect of a simultaneous administration of styrene and ethanol on NPS content and lipid peroxidation in rat liver and brain. Hepatic cytochrome P450 and cytochrome b5 content, aniline hydroxylase and aminopyrine N-demethylase activities as well as the two major urinary metabolites of styrene, mandelic and phenylglyoxylic acids were also measured. Groups of rats given ethanol for 3 weeks in a liquid diet were exposed, starting from the second week, to 326 ppm of styrene (6 h daily, 5 days a week, for 2 weeks). In control pair-fed animals, styrene produced about 30% depletion of brain NPS and 50% depletion of hepatic NPS. Subchronic ethanol treatment did not affect hepatic NPS levels, but caused 23% depletion of brain NPS. Concomitant administration of ethanol and styrene caused a NPS depletion in brain tissue in the order of 60%. These results suggest that in the rat, simultaneous exposure to ethanol and styrene may lead to considerable depletion of brain NPS. This effect is seen when both compounds are given on a subchronic basis, a situation which better resembles possible human exposure.

Effects of simultaneous administration of ethanol on styrene metabolism under fed and fasted conditions in the perfused rat liver

The purpose of this study was to clarify the simultaneous administration of ethanol on styrene metabolism in the perfused rat liver under fed and fasted conditions. Styrene uptake rate, production rate of styrene glycol, oxygen consumption rate, and changes in reduced pyridine nucleotide fluorescence were monitored in the perfused rat liver. The effects of ethanol on parameters of styrene metabolism were observed in rat livers under fed and fasted conditions: fed (group I), fasted (group II), and fasted with xylitol in the perfusate (group III). The simultaneous administration of ethanol and styrene significantly decreased styrene uptake rate, production rate of styrene glycol, and oxygen consumption rate, and produced significant reduction of pyridine nucleotide fluorescence as compared with the single administration of styrene in groups I and III. In contrast, the simultaneous administration of ethanol and styrene significantly increased the production of styrene glycol and oxygen consumption as compared with the single administration of styrene in group II. Significant effects on the styrene uptake rate and the reduced pyridine nucleotide fluorescence were observed with regard to factors of both nutritional status and the interaction between ethanol and nutritional status by two-way analysis of variance. These findings showed that the effects of ethanol on styrene metabolism in the liver were dependent upon the nutritional status of the animal. The fed and fasted conditions affected the effect of ethanol on styrene metabolism by changing the supply of NADPH to the mixed-function oxidase system. In conclusion, ethanol suppressed styrene metabolism in the fed condition, but enhanced it in the fasted condition. This phenomenon should be considered in the prevention of occupational hazard of styrene exposure in industrial workers with alcohol drinking habits and nutritional problems.

Exposure to styrene and chronic health effects: mortality and incidence of solid cancers in the Danish reinforced plastics industry

OBJECTIVES

To study the occurrence of non-malignant diseases and solid cancers in workers exposed to styrene in the Danish reinforced plastics industry.

METHODS

All 36,610 workers of 386 reinforced plastics companies and 14,293 workers not exposed to styrene from similar industries were followed up from 1970 to 1990. This industry is characterised by simple exposure conditions, exposure to high concentrations of styrene, and a high proportion of small companies, and the exposure assessment was based on experts' classification on a company level. The mortality from non-malignant causes and the incidence of solid cancers were compared with the national rates. Poisson models were used for internal comparisons.

RESULTS

A total of 3031 deaths and 1134 newly diagnosed cases of solid cancer were reported in the workers in the reinforced plastics industry. In companies where 50% or more of the workers produced reinforced plastics an increased mortality rate ratio (MRR) for degenerative disorders of the nervous system (multiple sclerosis, parkinsonism, and motor neurone disease; MRR 1.8, 16 cases, 95% confidence interval (95% CI) 0.9-3.8) and an increased incidence rate ratio (IRR) for pancreatic cancer (IRR 2.2, 17 cases, 95% CI 1.1-4.5) was found. For both disease categories increased occurrence was also found among long term workers, workers of the 1960s (the period with the highest exposure to styrene), and workers with a latent period of more than 10 years after the start of employment. No other non-malignant diseases or solid cancers showed these patterns.

CONCLUSION

The findings have to be interpreted with caution, due to the company based exposure assessment, but the possible association between exposures in the reinforced plastics industry, mainly styrene, and degenerative disorders of the nervous system and pancreatic cancer, deserves attention.

The enantioselective metabolism of 4-isopropenyltoluene in rabbits

4-Isopropenyltoluene (8) was administered orally to rabbits and the following four optically active metabolites, 2-(p-tolyl)propanoic acid (10), p-(1-carboxyethyl)benzoic acid (11), 2-hydroxy-2-(p-tolyl)propanoic acid (12), and 2-(p-tolyl)-1,2-propanediol (13) were isolated from urine in addition to an optically inactive metabolite, 4-isopropenylbenzoic acid (9). The enantiomeric ratios of the metabolites 10 and 11 were respectively R/S = 33:67 and 39:61 (S predominance), whereas those of the metabolites 12 and 13 possessing a tertiary hydroxyl group were R/S = 77:23 and 84:16 respectively (R predominance). The presumed metabolic pathways of 8 in rabbits leading to these metabolites are discussed.

Solvent-induced ototoxicity in rats: an atypical selective mid-frequency hearing deficit

Most previous reports of ototoxicity following exposure to several volatile organic solvents have restricted testing to the low- and mid-frequencies (2-20 kHz) of the hearing range in the rat (0.25-80 kHz). We report here that inhalation exposure to styrene, mixed xylene, toluene, and 1,1,2-trichloroethylene resulted in hearing dysfunction only in the mid-frequency range and spared function at lower and higher frequencies. Adult male Long Evans rats were exposed via inhalation (whole body) in flow-through chambers. The following exposures were used: styrene, 1600 ppm; 1,1,2-trichloroethylene, 3500 ppm; toluene, 2500 ppm; mixed xylenes, 1800 ppm (N = 7-8 per group, 8 h/day for 5 days), and n-butanol, 4000 ppm (N = 10/group, 6 h/day for 5 days). Testing of auditory function was conducted 5 to 8 weeks after exposure using reflex modification audiometry (RMA). RMA thresholds were determined for frequencies from 0.5 to 40 kHz. Results indicated increased RMA thresholds for the mid-frequency tones (e.g., 8 and 16 kHz), but not higher or lower tones, for all solvents except n-butanol. Toluene and xylene also increased thresholds at 24 kHz. These data indicate that for those solvents reported thus far to cause hearing loss, the deficit is restricted to mid-frequencies in rats.

A physiologic pharmacokinetic model for styrene and styrene-7,8-oxide in mouse, rat and man

Concern about the carcinogenic potential of styrene (ST) is due to its reactive metabolite, styrene-7,8-oxide (SO). To estimate the body burden of SO resulting from various scenarios, a physiologically based pharmacokinetic (PBPK) model for ST and its metabolite SO was developed. This PBPK model describes the distribution and metabolism of ST and SO in the rat, mouse and man following inhalation, intravenous (i.v.), oral (p.o.) and intraperitoneal (i.p.) administration of ST or i.v., p.o. and i.p. administration of SO. Its structure includes the oxidation of ST to SO, the intracellular first-pass hydrolysis of SO catalyzed by epoxide hydrolase and the conjugation of SO with glutathione. This conjugation is described by an ordered sequential ping-pong mechanism between glutathione, SO and glutathione S-transferase. The model was based on a PBPK model constructed previously to describe the pharmacokinetics of butadiene with its metabolite butadiene monoxide. The equations of the original model were revised to refer to the actual tissue concentration of chemicals instead of their air equivalents used originally. Blood:air and tissue:blood partition coefficients for ST and SO were determined experimentally and have been published previously. Metabolic parameters were taken from in vitro or in vivo measurements. The model was validated using various data sets of different laboratories describing pharmacokinetics of ST and SO in rodents and man. In addition, the influences of the biochemical parameters, alveolar ventilation and blood:air ventilation and blood:air partition coefficient for ST on the pharmacokinetics of ST and SO were investigated by sensitivity analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Review of styrene and styrene oxide long-term animal studies

Eleven long-term toxicity studies were reviewed on styrene and five on styrene oxide in an effort to evaluate the potential carcinogenic activity of these chemicals in animals. The styrene studies included inhalation exposure (rats, mice, guinea pigs, and rabbits), intragastric gavage (rats and mice), drinking water (rats), and intraperitoneal injection (rats), while styrene oxide exposure was via intragastric gavage (rats and mice) or skin painting (mice). Each study was reviewed and evaluated for details and adequacy of design, adequacy of reported data, and interpretation. The results of this review are 1. There was no convincing evidence of carcinogenic activity of styrene in animals, although many of the studies were considered inadequate. 2. Styrene oxide was carcinogenic to the forestomach of both sexes of rats and mice after gavage exposure and was associated with an increase in liver neoplasms in male mice in one study. No carcinogenic activity was observed in mice after dermal exposure (skin paint). 3. None of the studies of styrene or styrene oxide reported here are well suited for extrapolating potential carcinogenic activity of either compound to humans because all have deficiencies in design, conduct, interpretation, or utilized a less than ideal route of exposure. A chronic state-of-the-art inhalation study is needed to evaluate this aspect of hazard assessment.

Phase I clinical trial of an injectable contraceptive for the male

Earlier studies on the rat and the monkey had demonstrated that an injection of styrene maleic anhydride (SMA) in a solvent vehicle of dimethyl sulphoxide (DMSO) into the lumen of the vas deferens is toxicologically safe and has contraceptive action. Phase I clinical trial was therefore undertaken on 38 male volunteers giving varying doses of SMA, ranging between 5 mg and 140 mg, into each vas deferens. A dose of 70 mg is the predicted therapeutic dose based on animal data. That the compound is within the vas deferens lumen during the period of the safety assessment is inferred from the effect on the spermatozoa count in ejaculates which reach azoospermic levels in the higher dose ranges. The treatment is well tolerated with only minimal side effects in a few cases and no long-term adverse effects.