Modulation of benzene toxicity by an interferon inducer (6MFA)

Studies on hepatic oxidative stress and antioxidant defence system during chloroquine/poly ICLC treatment of Plasmodium yoelii nigeriensis infected mice

Reactive oxygen species are important mediators of tissue injury during malaria infection. The status of hepatic oxidative stress and antioxidant defence indices were studied during Plasmodium yoelii nigeriensis (P. y. nigeriensis) infection and chloroquine/ polyinosinic-polycytidylic acid stabilized with polylysine and carboxymethylcellulose (poly ICLC) treatment of infected mice. P. y. nigeriensis infection resulted in a significant increase in oxidative stress indices viz., xanthine oxidase and rate of lipid peroxidation (LPO). This was accompanied by a highly significant increase in antioxidant defence indices viz., reduced glutathione (GSH) and glutathione reductase while superoxide dismutase (SOD) and catalase showed a highly significant decrease with respect to normal mice. Chloroquine treatment of infected mice caused a decrease in parasitaemia which was associated with restoration of indices altered during infection towards normalization. Poly ICLC treatment of infected mice caused no change in blood parasitaemia but resulted in a significant increase in GSH, glutathione reductase, SOD and catalase with respect to infected mice. Combination therapy of chloroquine and poly ICLC resulted in clearance of parasitaemia and restoration of all oxidative stress and antioxidant defence indices to normal levels.

Moderate protective effect of 6-MFA, a microbial metabolite obtained from Aspergillus ochraceus on immunological liver injury in mice

Hepatoprotective effect of 6-MFA, obtained from fungus Aspergillus ochraceus ATCC 28706, was evaluated by employing three different immunological liver injury mice models. The first liver injury model was induced by injecting anti-basic liver protein (BLP) antibody into mice previously immunised with rabbit IgG (RGG). The other models were simulated by injecting antiliver specific protein (LSP) antibody or by injecting bacterial lipopolysaccharide (LPS) into mice pretreated with Corynebacterium parvum (C. parvum). 6-MFA treatment inhibited the increased transaminases (GOT and GPT) activities and showed a tendency to inhibit the histopathological changes of the liver in all the models studied. Furthermore, 6-MFA treatment inhibited deoxycholic acid induced transaminase release from cultured rat hepatocytes in vitro, but failed to affect the formation of hemolytic plaque forming cells in immunised mice spleens and hemolytic activity of guinea pig complement in immunohemolytic reaction. Our findings, therefore, suggested that the moderate hepatoprotective effect of 6-MFA could be related to it's protective effect on hepatocyte plasma membrane rather than the direct inhibitory effects on the antibody formation and/or complement activity.

Benzene--a review of the literature from a health effects perspective

A literature review of the impact on human health of exposure to benzene was conducted. Special emphasis in this report is given to the health effects reported in excess of national norms by participants in the Benzene Subregistry of the National Exposure Registry--people having documented exposure to benzene through the use of benzene-contaminated water for domestic purposes. The health effects reported in excess (p < or = .01) by some or all of the sex and age groups studied were diabetes, kidney disease, respiratory allergies, skin rashes, and urinary tract disorders; anemia was also increased for females, but not significantly so.

Immunoprevention of cancer poses a challenge to pharmacological research

The evolving understanding of the molecular mechanisms of carcinogenesis establishes that the long latency period would offer numerous opportunities for intervention before the final step of fully developed malignancy has been reached. Immunoprevention of cancer may be a new approach to cancer control, by eliminating the cellular minimal deviations that are seen in the early phases of carcinogenesis. Available results of immunotherapy of preneoplastic lesions and data on anticarcinogenesis with immunoregulators in experimental models are in good accordance with theoretical expectations. However, clinical research on immunoregulators still focuses on the treatment of advanced cancer. The major problem hampering a wider application of immunoregulators in cancer prevention is the possibility of potential adverse effects, which are largely unknown. The promotion of future research in this area is essential. Moreover, the ethical issues of intervention trials in cancer must be discussed, by considering the potential psychological and social consequences.

Interferons in precancer and cancer prevention: where are we?

Clinical research on interferons (IFN) still focuses on the treatment of advanced cancer. The research strategy eventually must be reevaluated. The cellular minimal deviations that are seen in early phases of carcinogenesis might be the most rational target for immune interventions. That biologic response modifiers have considerable capacity to prevent induction and development of malignant neoplasias has been demonstrated in several animal systems. Even the few clinical studies available at present on the treatment of preneoplastic lesions with IFN have definitely shown more success than those involving treatment of advanced tumors. In addition, there is experimental evidence that IFN might be suitable candidates for immunoprevention. The major problems hampering a wider application of IFN in immunoprevention is that they cause adverse effects. Unfortunately, we do not know much about the specific mechanisms involved in the immune control of human tumor development during the initial and the latency phases of carcinogenesis. More research is needed in this area. In this article the state of the art of using IFN for treating preneoplastic lesions is reviewed, and also we report some of our experimental results on IFN and anticancerogenesis.

Immunostimulating effects of protein A in immunosuppressed aflatoxin-intoxicated rats

Aflatoxin B1, the potent carcinogenic compound produced by the Aspergillus flavus group of fungi on food and feed, induces immunosuppressive effects in rodents. In this communication, we report an immunomodulatory approach to abrogate aflatoxin B1-induced immunotoxicity in rats using protein A of Staphylococcus aureus Cowan 1. We have earlier demonstrated that protein A can protect the animals from toxicities induced by a number of drugs, chemicals and toxins. In the present study various combinations of aflatoxin B1 exposure and protein A treatment in animals were used. It was observed that protein A could provide protection to animals from aflatoxin B1-induced immunotoxicity, as measured by a battery of tests assessing cell-mediated immunity (CMI) profile of the host. Various parameters showing suppression of CMI following aflatoxin B1 exposure were reverted back towards normalcy in protein A-treated animals. It is concluded that protein A may prove to be a useful agent to protect the host from aflatoxin immunotoxicity, in view of its stimulatory effects on various immune functions even after their initial depression due to aflatoxin B1.

Acrylamide induced immunosuppression in rats and its modulation by 6-MFA, an interferon inducer

In the present communication, we describe acrylamide (ACR) induced immunotoxicity and its modulation by an interferon inducer, the 6th mycelial fraction acetone (6-MFA) of Aspergillus ochraceus ATCC 28706. ACR administration to rats produced a significant decrease in the weight of spleen (p < 0.001), thymus (p < 0.001) and mesenteric lymph nodes (p < 0.05). A decrease in cellularity of spleen (p < 0.001), thymus (p < 0.001), bone marrow (p < 0.001) and circulating blood lymphocyte population (p < 0.001) was also recorded. ACR suppressed the humoral as well as cell mediated immunity as assessed by erythrocyte antibody complement (EAC)-rosettes (p < 0.001), hemagglutination titre (p < 0.001), PFC (p < 0.001) and the delayed type hypersensitivity response against sheep red blood cells (SRBC, p < 0.001). ACR treated immunosuppressed rats when treated with 6-MFA restored the circulating lymphocyte number to the normal level and a partial recovery in the weight of spleen and thymus. Potentiation of EAC-rosettes, hemagglutination titre, IgM-PFC and DTH response against SRBC was observed. It is concluded that 6-MFA ameliorate the ACR induced toxicity. This study may be of significance in prevention of ACR toxicity.

The modulating activity of interferon on benzo(a)pyrene bioactivation and clastogenesis in mice

Acute intraperitoneal administration of benzo(a)pyrene (80 mg/kg b.wt.) resulted in time-dependent increases in chromosome aberrations, especially of break-type in the bone marrow of treated mice. Pretreatment with murine interferon-alpha/beta (5 x 10(4) IU daily for two days) caused a significative decrease in the cytogenetic response in vivo of benzo(a)pyrene (up to 51%) and a stabilization of aberrant cells up to 48 hr. The administration of murine interferon-alpha/beta gave rise to a marked depression of microsomal monooxygenase system after 24 hr, as exemplified by the significant reduction of cytochrome P450 content as well as deethylation of ethoxyresorufin. Interferon treatment delayed the obtainment of basal levels of oxidative metabolism to approximately 30 hr. After interferon plus benzo(a)pyrene treatment, ethoxyresorufin O-deethylase activity showed a reduction up to 60%; levels comparable to benzo(a)pyrene treated group were restored by 48 hr. Immunoblotting analysis confirmed reduced CYP1A1 level. Results suggest that the inhibition of benzo(a)pyrene hepatic metabolism by interferon was reflected by changes in its clastogenic activity. Persistence of low level of chromosome aberration at 48 hr may be reconducible to other interferon sensitive processes than effects on hepatic mixed-function oxidase system, such as DNA repair activity and cell proliferation.

Modulation of benzene induced toxicity by protein A

Administration of benzene (i.p. 1.0 mL/kg body weight) for 3 consecutive days produced leucopenia and lymphocytopenia in female albino rats. In addition, the total iron content, lipid peroxidation and superoxide dismutase activity of the liver and bone marrow were significantly (P < 0.001) increased. Low molecular weight (LMW) bleomycin-detectable iron accumulated only in bone marrow. Prior administration of Protein A (PA), a multipotent immunostimulant and interferon inducer (60 micrograms/kg body weight, i.v. twice weekly for 2 weeks), ameliorated most of the adverse effects of benzene. PA restored the changes in hepatic histological architecture, reversed leucopenia and superoxide dismutase activity, lipid peroxidation, total iron content and LMW iron content of bone marrow were normalized. Isozymes of glutathione-S-transferase (alpha, pi, mu) which decreased following benzene exposure increased in PA pretreated benzene exposed rats. This study suggests that pretreatment with PA modulates the toxicity of benzene.

Effect of zinc on immune functions and host resistance against infection and tumor challenge

The effect of zinc treatment on immune function and resistance against infection and tumor challenge was studied in mice. Swiss albino mice were treated with zinc acetate (3 mg/kg body weight) in one or two intraperitoneal injections. Various immune function assays were performed in treated animals. Zinc treatment to normal animals caused potentiation of T-lymphocyte and macrophage functions. Zinc treatment was also found to increase host resistance against Candida albicans and Semliki Forest virus infections. Increased resistance against endotoxin shock and Ehrlich's ascites tumor challenge was also observed in zinc treated animals. It can be stated from this study that zinc treatment potentiates the cell mediated immunity and host resistance against infection and tumor challenge.

Accumulation of low molecular weight (bleomycin detectable) iron in bone marrow cells of rats after benzene exposure

An accumulation of low molecular weight (LMW) bleomycin detectable iron in the bone marrow was observed after administration of benzene (IP 0.5 ml/kg, daily) for 5 and 10 days in female albino rats. However, this LMW iron was not detectable in the bone marrow of rats from the control group. Studies of bone marrow fractionation showed that the maximum accumulation of this LMW iron was in the mitochondrial fraction. An increase in the activity of superoxide dismutase and lipid peroxidation was also noticed in the benzene exposed groups.

Modulation of benzene toxicity by polyinosinic-polycytidilic acid, an interferon inducer

Repeated intraperitoneal administration of benzene (1.0 ml/kg body wt.) for 3 days produced leucopenia, lymphocytopenia and significantly decreased body wt. (P less than 0.001) and organ weights of thymus (P less than 0.001) and spleen (P less than 0.001) in female albino rats. Total iron content, lipid peroxidation and superoxide dismutase activity of the liver and bone marrow were significantly increased as a result of benzene exposure. Low molecular weight (LMW) bleomycin detectable iron content was accumulated in bone marrow, whereas hepatic LMW iron was not detectable after benzene intoxication to rats. Prior administration of single dose (250 micrograms/100 g body wt.) of Poly IC, an interferon inducer with immunomodulating potential was found to be ameliorate some of the adverse effects of benzene as well as restoration of hepatic architecture histologically. Superoxide dismutase activity, lipid peroxidation, total iron content and LMW iron content (bone marrow) were normalised. Pretreatment of animals with Poly IC was able to enhance the SRBC antibody titre in benzene-treated animals. This study suggests that the beneficial effects of Poly IC in the amelioration of the acute toxicity of benzene has clinical significance.

Protection against carbon tetrachloride-induced hepatotoxicity by protein A

Protection from carbon tetrachloride (CCL4)-induced hepatotoxicity by protein A was assessed histologically in rats. Carbon tetrachloride exposure produced swollen, vacuolated and necrotic cells in the centrilobular region of the hepatocyte in rats. Animals given protein A prior to and during CCL1 treatment showed a complete absence of hepatic lesions. Our study showed that protein A, a potent immunomodulator, has the potential to reduce liver injury caused by carbon tetrachloride, a known hepatotoxin in the rat.

Quantitation of ozone-induced lung lesion density after treatment with an interferon inducer or an anti-interferon antibody

Inhalation of ozone by experimental animals produces activation of lymphocytes in the mediastinal lymph node complex. Both the number and functional reactivity are affected, with evidence of blastic transformation in T cell but not B cell areas of the nodes. In the present work we determine the extent that modulation of a possible product of immune system activation, interferon, is capable of influencing the way that experimental animals respond to zone. Outbred CD-1 mice were treated with an interferon inducer, poly I:C, or with an anti-interferon antibody while being exposed to ozone at a concentration of 0.7 or 0.9 ppm for 20 h per day for 4 days. Interferon induction produced a significant reduction in lesion volumes in both exposure groups, while anti-interferon produced the opposite effect. Less alveolar damage was observed in interferon-induced, ozone-exposed animals than in animals exposed to ozone alone. In contrast, anti-interferon-treated, ozone-exposed animals showed larger lesions which extended to more peripheral structures and were more extensively infiltrated with neutrophilic leukocytes. These results show that interferon induction protects against zone-mediated lung damage. They also suggest that cells are activated during ozone inhalation which mitigate the effects of ozone on the lung by secretion of interferon.

Petroleum hydrocarbon toxicity in vitro: effect of n-alkanes, benzene and toluene on pulmonary alveolar macrophages and lysosomal enzymes of the lung

The in vitro effects of straight chain alkanes (nC6-nC10), benzene and toluene on pulmonary alveolar macrophages (PAM) of rats and rabbits was studied. The concentrations used ranged from 0.02 to 1.0 mM. All hydrocarbons used in the study were cytotoxic to isolated cultured PAM cells in a dose-dependent manner. The LC50 for these hydrocarbons towards rat PAM cells was estimated to be 1.0 mM for nC8, 2 mM for nC7, 5 mM for nC9 and 10 mM for nC6, nC10, benzene and toluene. Rabbit PAM cells were more sensitive to the hydrocarbons, resulting in and LC50 half that for rat PAM cells. Hydrocarbons also caused extracellular release of the lysosomal enzymes cathepsin D (EC 3.4.23.5) and cathepsin B (EC 3.4.22.1) in a manner corresponding with cell damage. There was more cathepsin D activity released from cells than cathepsin B. In addition, hydrocarbons also caused the release of cathepsin B and D from isolated lysosomes, and there was 10-15% more enzyme activity released in the culture medium of lysosomes exposed to concentrations of 0.5 and 1.0 mM compared to PAM cell cultures of either rats or rabbits. Hydrocarbons also caused loss of cell respiration and stimulated a dose-dependent and a time-dependent increase in lipid peroxidation. The two alkanes nC7 and nC8 caused the greatest increase in lipid peroxidation and the greatest loss of cell respiration. The results indicate that there is a relationship between chain length of alkanes and their cytotoxicity to PAM cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Recent advances in the metabolism and toxicity of benzene

Benzene is a heavily used industrial chemical, a petroleum byproduct, an additive in unleaded gas, and a ubiquitous environmental pollutant. Benzene is also a genotoxin, hematotoxin, and carcinogen. Chronic exposure causes aplastic anemia in humans and animals and is associated with increased incidence of leukemia in humans and lymphomas and certain solid tumors in rodents. Bioactivation of benzene is required for toxicity. In the liver, the major site of benzene metabolism, benzene is converted by a cytochrome P-450-mediated pathway to phenol, the major metabolite, and the secondary metabolites, hydroquinone and catechol. The target organ of benzene toxicity, the hematopoietically active bone marrow, metabolizes benzene to a very limited extent. Phenol is metabolized in the marrow cells by a peroxidase-mediated pathway to hydroquinone and catechol, and ultimately to quinones, the putative toxic metabolites. Benzene and its metabolites appear to be nonmutagenic, but they cause myeloclastogenic effects such as micronuclei, chromosome aberrations, and sister chromatid exchange. It is unknown whether these genomic changes, or the ability of the quinone metabolites to form adducts with DNA, are involved in benzene carcinogenicity. Benzene, through its active metabolites, appears to exert its hematological effects on the bone marrow stromal microenvironment by preventing stromal cells from supporting hemopoiesis of the various progenitor cells. Recent advances in our understanding of the mechanisms by which benzene exerts its genotoxic, hematotoxic, and carcinogenic effects are detailed in this review.