Alterations in interleukin-6 production by LPS- and Con A-stimulated mixed splenocytes, spleen macrophages and lymphocytes in prenatally diazepam-exposed rats

In utero exposure to diesel exhaust particles, but not silica, alters post-natal immune development and function

Our understanding of the impact of in utero exposure to PM on post-natal immune function and the subsequent response to PM exposure is limited. Similarly, very few studies have considered the effect of exposure to PM from different sources. Thus, the aim of this study was to examine how in utero exposure to PM from different sources effects the post-natal response to pro-inflammatory and immune stimuli. C56BL/6J pregnant mice were exposed intranasally on gestational day (E)7.5, E12.5 and E17.5-50 μg of diesel exhaust particles (DEP), silica or saline. At 4-weeks post-natal age, sub-groups of male and female mice were exposed intranasally to 50 μg of DEP or saline. Lung inflammatory responses were assessed 6 h later by quantifying inflammatory cells and cytokine production (MCP-1, MIP-2, IL-6). In separate groups of mice, the spleen was harvested to quantify B and T cell populations. Splenocytes were isolated and exposed to lipopolysaccharide or poly I:C for assessment of cytokine production. Exposure to DEP in utero decreased %CD1d^highCD5+ B cells in female mice and IFN-γ production by splenocytes in both sexes. Male mice had elevations in macrophage and lymphocyte numbers in response to DEP whereas female mice only had elevated IL-6, MCP-1 and MIP-2 levels. In utero exposure to silica had no effect on these measures. These data suggest that in utero exposure to PM alters immune development and post-natal immune function. This response is dependent on the source of PM, which has implications for understanding the community health effects of exposure to air pollution.

Delayed developmental immunotoxicity of prenatal benzodiazepines

Treatment of pregnant rats with low doses of classical benzodiazepines (BDZ, e.g. 1.25 mg diazepam/kg body weight) or a peripheral type BDZ receptor (PBR) agonist between gestational days 14 and 20 has been shown to result in a long-lasting depression of cellular and humoral immune responses in the offspring. Considerable alterations in mitogen-stimulated cytokine production in rats exposed to diazepam prenatally have now been observed: TNF-alpha liberation by splenocytes of diazepam-exposed rats was reduced at 2 wk of age and increased above control values at 8 wk, and interleukin (IL)-6 was depressed in the offspring at 2 and 8 wk of age. IL-1 was diminished during post-weaning and adult periods in male offspring but only in adult life in female offspring. In contrast, T-cell derived IL-2 was decreased during the postnatal period and normalized in adulthood. Prostaglandin E(2) (PGE(2)), which is known to down-regulate tumour necrosis factor-alpha (TNF-alpha) was increased and interferon-gamma (IFN-gamma), which stimulates TNF-alpha release, was depressed in 2-wk-old offspring that had been treated prenatally. Release of PGE(2) and IFN-gamma was still altered in young adulthood. While the initial action on the foetal immune system remains unknown, an interaction of the drugs with the PBR is suggested by the effectiveness of the PBR agonist and by altered characteristics of PBR (i.e. a decreased B(max) of [(3)H]PK 11195 binding to macrophage membranes of 8-wk-old offspring and an increased Kd of spleen cell membranes of 2-wk-old offspring).

Mice with heterozygous deficiency of lipoic acid synthase have an increased sensitivity to lipopolysaccharide-induced tissue injury

Alpha-lipoic acid (1, 2-dithiolane-3-pentanoic acid; LA), synthesized in mitochondria by LA synthase (Lias), is a potent antioxidant and a cofactor for metabolic enzyme complexes. In this study, we examined the effect of genetic reduction of LA synthesis on its antioxidant and anti-inflammatory properties using a model of LPS-induced inflammation in Lias+/- mice. The increase of plasma proinflammatory cytokine, TNF-alpha, and NF-kappaB at an early phase following LPS injection was greater in Lias+/- mice compared with Lias+/+ mice. The circulating blood white blood cell (WBC) and platelet counts dropped continuously during the initial 4 h. The counts subsequently recovered partially in Lias+/+ mice, but the recovery was impaired totally in Lias+/- mice. Administration of exogenous LA normalized the recovery of WBC counts in Lias+/- mice but not platelets. Enhanced neutrophil sequestration in the livers of Lias+/- mice was associated with increased hepatocyte injury and increased gene expression of growth-related oncogene, E-selectin, and VCAM-1 in the liver and/or lung. Lias gene expression in tissues was 50% of normal expression in Lias+/- mice and reduced further by LPS treatment. Decreased Lias expression was associated with diminished hepatic LA and tissue oxidative stress. Finally, Lias+/- mice displayed enhanced mortality when exposed to LPS-induced sepsis. These data demonstrate the importance of endogenously produced LA for preventing leukocyte accumulation and tissue injury that result from LPS-induced inflammation.

The comparative immunotoxicity of five selected compounds following developmental or adult exposure

It is well established that human diseases associated with abnormal immune function, including some common infectious diseases and asthma, are considerably more prevalent at younger ages. Although not established absolutely, it is generally believed that development constitutes a period of increased immune system susceptibility to xenobiotics, since adverse effects may occur at lower doses and/or immunomodulation may be more persistent, thus increasing the relative risk of xenobiotic exposure to the immunologically immature organism. To address this issue, a brief overview of immune maturation in humans is provided to demonstrate that functional immaturity alone predisposes the young to infection. Age-dependent differences in the immunotoxic effects of five diverse compounds, diethylstilbestrol (DES), diazepam (DZP), lead (Pb), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and tributyltin oxide (TBTO), which have undergone adult and developmental immunotoxicity testing in rodents, are then reviewed, as are human data when available. For all five chemicals, the developing immune system was found to be at greater risk than that of the adult, either because lower doses produced immunotoxicity, adverse effects were more persistent, or both.

Evolution of the thymus size in response to physiological and random events throughout life

During embryogenesis and in the early stages of life, the thymus is a crucial organ for the generation of the T cell repertoire. T cells are generated from hematopoietic stem cells already differentiated to precursor T cells in the bone marrow. These cells enter the thymus guided by chemotactic factors secreted by this organ. The complex maturation process takes place that ensures self-tolerance and homeostasis. Thymocytes that show autoreactivity do not leave the thymus, but rather die by apoptosis. The final percentage of mature T cells that survive to migrate from the thymus to the periphery is very low: at most 5%, under optimal conditions. The highest migration occurs in childhood and adulthood, at least in mice and humans; however, it declines throughout life and is minimal in the elderly. Under normal circumstances, the thymus commences involution soon after birth, and this involution correlates with the capacity to export mature T cells to the periphery. Hormones, cytokines, and neurotransmitters all play a role in this age-associated process, but the reasons for and mechanisms of this involution remain unknown. Apart from physiological conditions that change throughout life and govern age-related thymus evolution, random states and events provoked by intrinsic or extrinsic factors can induce either thymus involution, as in reversible transient thymic hypoplasias, or thymic hyperplasias. The age-associated involution, unlike transient involutions, follows a regular pattern for all individuals, though there are clear differences between the sexes. Nevertheless, even the age-associated involution seems to be reversible, raising the possibility of therapeutic strategies aimed at enhancing thymus function in the elderly.

Developmental toxicity but no immunotoxicity in the rat after prenatal exposure to diethylstilbestrol

Studies with dioxins and PCB's have shown that the developing immune system may be especially vulnerable to xenobiotics during the perinatal period. However, current guidelines for reproductive toxicity testing do not include immune parameters. In the present study, we have explored the usefulness of including immune parameters within the prenatal developmental toxicity study in rats, using the treatment protocol as described in the OECD 414 developmental toxicity test guideline. In addition, the experimental protocol was enhanced by including ten dose groups to facilitate dose-response analysis. Diethylstilbestrol (DES) was used as the model compound, as it is known to be toxic both for embryofetal development and for the immune system. The results show developmental toxicity in terms of decreased fetal survival and decreased pup body weight in the presence of reduced maternal food consumption and reduced body weight gain. However, immune parameters, including histopathology, hematology, and antibody responses to sheep red blood cells (SRBC) in pups at 4 weeks of age were uncompromised. It is speculated that rather than the prenatal exposure protocol used here, the generation study design with both pre- and postnatal exposure may be preferable as a general screen to detect developmental immunotoxic injury after xenobiotic exposure.

Diazepam effects of peritoneal macrophage activity and corticosterone serum levels in Balb/C mice

In the present experiment we investigate the effects of diazepam on macrophage activity and serum corticosterone levels in mice. Adult mice were treated with diazepam (1.5 mg/kg/day - group E) or with control solution (group C1) for 7 days; some animals were only handled, receiving no treatment (group C2). Oral onco-BCG was used for peritoneal macrophage activation. Diazepam treatment: 1-decreased macrophage spreading and phagocytosis; 2-decreased the concentrations of H2O2 spontaneously but not phorbol myristate-acetate-induced release. In relation to mice of group C1, diazepam treatment increased the serum levels of corticosterone. No differences were detected between data of groups C1 and C2 both for macrophage activity and serum corticosterone levels. The present data were explained on the basis of a synergistically action for diazepam through peripheral type binding sites (PBR) present in both adrenals and macrophages, stimulating adrenal glucocorticoid production and altering the macrophage cytokine network.

Effects of diazepam on Mycobacterium bovis-induced infection in hamsters

The in utero exposure of hamsters to low doses of diazepam results in impaired host defense against Mycobacterium bovis during adulthood. Delayed developmental immunotoxicity, however, represents a specific situation that might not be general. The present experiment was undertaken to investigate the effects of diazepam on hamster resistance to M. bovis using adult animals. The effects of diazepam treatment on serum cortisol levels were also studied. Adult hamsters (N = 10 for each group) were treated with diazepam (E1 = 1. 0, E2 = 2.0 or E3 = 3.0 mg kg-1 day-1 subcutaneously) or with control solution (C) for 30 days. Seven days after the beginning of the treatment, the animals received identical inoculum concentrations of M. bovis. Hamsters treated with the higher (2.0 and 3.0 mg kg-1 day-1) doses of diazepam exhibited: 1) increased granuloma areas in the liver (C = 1.81 +/- 1.39, E2 = 10.29 +/- 4.64 and E3 = 15.80 +/- 4.82) and lung (C = 0.54 +/- 0.55, E2 = 6.28 +/- 3.85 and E3 = 6.31 +/- 3.56) and 2) increased scores of M. bovis colony-forming units isolated from liver (C = 2.0, E2 = 3.0 and E3 = 3.5), lung (C = 1.0, E2 = 3.0 and E3 = 3.5) and spleen (C = 1.0, E2 = 2.5 and E3 = 4.0). These effects were dose dependent, and were not detected or were less severe in animals treated with the lowest (1.0 mg/kg) dose of diazepam as well as in those of the control group. Furthermore, diazepam treatment (3.0 mg kg-1 day-1 for 30 days) increased (E3 = 71.32 +/- 2.99; N = 10) the serum levels of cortisol compared to control hamsters (C = 22.61 +/- 2.75; N = 10). The present data, that demonstrate an impaired defense against M. bovis in adult hamsters treated with diazepam, were tentatively explained on the basis of a direct and/or indirect action of diazepam on the cytokine network. The effects may be related to stimulation of peripheral benzodiazepine receptor binding sites (PBR) by macrophages and/or lymphocytes, or they may be mediated by PBR stimulation of the adrenals.

Developmental, neuro and immunotoxic effects of perinatal diazepam treatment in rats

In utero exposure of rats to low dosages of diazepam (1.0-2.0 mg/kg) has been found to result in depression of the cellular and humoral immune responses during adulthood. Behavioral dysfunctions were also reported in infants from mothers with high benzodiazepine (BDZ) intake during pregnancy. The present experiment was undertaken to reconsider the potential action of diazepam during ontogeny in order to obtain further information about developmental processes using a refined methodology. Time-pregnant rats were treated subcutaneously with diazepam (2.0 mg/kg/day,: group E1) or with diazepam vehicle (group C1) from gestational day 14 to 20. Other dams (group E2) received the same BDZ dose from the 1st to the 21st day of lactation (weaning) or were not treated, remaining undisturbed in their home cages (group C2). The following results were obtained for animals perinatally treated with diazepam compared to groups C1 and C2: 1--increased time for testis descent and decreased time for vaginal opening (group E2); 2--no changes in the dates for ear end eye opening, or incisor tooth eruption (groups E1 and E2); 3--increased locomotor activity in the open-field (group E2) and/or in the plus maze (groups E1 and E2); 4--decreased levels of anxiety measured in the plus maze (groups E1 and E2); 5--decreased macrophage spreading and phagocytosis (groups E1 and E2). These results, which occurred in the absence of overt signs of maternal or fetal toxicity, demonstrate developmental, neuro- and immunotoxic effects of perinatal diazepam treatment in rats.

Effects of prenatal diazepam treatment on Mycobacterium bovis-induced infection in hamsters

In utero exposure of rats to low dosages of diazepam has been found to result in depression of cellular and humoral immune responses during adulthood, with marked changes in macrophage spreading and phagocytosis. The present experiment was undertaken to investigate the resistance of adult hamsters to Mycobacterium bovis after prenatal exposure to diazepam. Time-pregnant hamsters were exposed to diazepam (1.0 or 1.5 mg kg(-1) day(-1) subcutaneously) or vehicle from gestational day 9 to 15. A total of 36 different litters (12 of them control and 12 for each experimental group) born after a 16/17-day gestation were used. One male from each litter was infected twice with identical inoculum concentrations of M. bovis at 75 and 107 days of age. This infection model involves the participation of macrophages and T and B cell populations. The animals prenatally exposed to the higher (1.5 mg/kg) dose of diazepam exhibited: (1) increased weight loss, (2) increased mortality, (3) increased granuloma areas measured in the liver, lung and spleen, (4) increased spleen weight, and (5) increased scores of M. bovis colony forming units (CFU) isolated from liver, lung and spleen. These effects were dose-dependent, and were not detected or were less severe in animals treated with the lower (1.0 mg/kg) dose of diazepam as well as in those of the control group. The present data demonstrate an impaired defence against M. bovis in adult hamsters after in utero exposure to a dosage of 1.5 mg/kg of diazepam.

Cypermethrin-induced alteration of thymocyte distribution and functions in prenatally-exposed rats

The synthetic pyrethroid insecticide, cypermethrin (50 mg/kg) was given during gestation to pregnant rats by gavage in corn oil. Prenatal cypermethrin exposure induced a significant decrease in the absolute number of all thymocyte subsets during the first 30 days after birth, being the double negative CD4-CD8-, single positive CD4 and CD8 T cells preferentially affected. Later on day 60 and 90 double positive CD4+CD8+ and single positive thymocytes gradually recovered, while the total number of CD4 CD8 cells was increased. Moreover, thymocytes from rats prenatally exposed to cypermethrin showed an impaired ability to proliferate in response to different doses of Concanavalin A (ConA) and human recombinant interleukin-2 (hrIL-2) and to produce and/or release IL-2. Overall, our results indicate that cypermethrin administered during prenatal period can affect multiple steps in thymocyte differentiation pathways resulting in an altered cell subset distribution and an impairment of thymocyte functions.

Inhibition of nitric oxide (NO.) production in murine macrophages by flavones

The effect of flavone (2-phenylbenzopyran-4-one) and three amino-substituted flavones on the production of nitrite by murine activated peritoneal macrophages was studied in vitro. Activated peritoneal macrophages obtained from mice pre-treated with concanavalin A (Con A) (in vivo), after exposure in vitro to lipopolysaccharide (LPS) at a concentration of 100 ng/ml, produced nitrite (20.3 +/- 2.5 nmol/10(6) cells), as measured after 24 hr by the Griess reaction. Stimulation of production of nitrite was inhibited by NG-monomethyl-L-arginine, suggesting that nitrite was formed via nitric oxide (NO.) as a product of metabolism of arginine. Stimulation was inhibited by flavone and the aminoflavones (20-100 microM). 3'-amino-4'-hydroxyflavone was the most potent inhibitor of nitrite production. Genistein (5,7-dihydroxy- 3-(4-hydroxy-phenyl)-4H-1-benzopyran-4-one) also inhibited production of nitrite, by a mechanism that appears not to involve protein tyrosine kinases. These results suggest that the flavones can modulate the immune responses and the inflammatory reactions by controlling production of nitric oxide.

Impaired host resistance to Trichinella spiralis as a consequence of prenatal treatment of rats with diazepam

In utero exposure of Long Evans rats to low dosages of diazepam has previously been found to result in depression of cellular and humoral immune responses until adulthood, with marked changes in cytokine release by splenocytes and splenic macrophages. In order to assess the significance of these alterations in immune cells with regard to host resistance, we investigated the resistance of adult offspring towards Trichinella spiralis. Time-pregnant rats were treated with diazepam (1.25 mg/kg/day) or vehicle from gestational day 14 to 20. Male offspring were infected with T. spiralis at 2 months of age. This infection model tests the participation of T- and B-cell populations and of macrophages. Prenatally diazepam-exposed animals exhibited an impaired defence towards T. spiralis. The number of muscle larvae was increased as determined in digested carcasses and by morphometric analysis of the tongue. Moreover, antibody titers were altered, i.e., IgG was decreased and IgA was elevated in the prenatally diazepam-exposed group. These results demonstrate an impaired defense towards T. spiralis in adult rats after prenatal exposure to diazepam.

Diazepam treatment of pregnant rats differentially affects interleukin-1 and interleukin-2 secretion in their offspring during different phases of postnatal development

Treatment of pregnant Long Evans rats with benzodiazepines was found to cause alterations in cellular immune responses in their offspring. We now report on changes in interleukin-1 (IL-1) and IL-2 secretion which were analyzed in rats from birth until 12 weeks. Time-pregnant rats were treated with diazepam (1.25 mg/kg/day subcutaneously) from gestational day 14 to 20. Lipopolysaccharide-stimulated release of macrophage-derived IL-1 by spleen cells, determined on D10.G4.1 cells, remained in the control range during the preweaning period (postnatal day 6-28), then decreased in prenatally diazepam-exposed offspring, significantly in males during the postweaning period (postnatal day 34-61) and in both sexes in adults (postnatal day 62-83). Concanavalin A-stimulated release of T lymphocyte-derived IL-2 from spleen cells, determined on CTLL-2 cells, was reduced in male and female offspring during preweaning (postnatal day 3-28) and postweaning (postnatal day 33-55) periods and normalized in adulthood (postnatal day 60-84). The percentage of IL-2 receptor expressing (CD25+) cells was unaffected. From these and our earlier data it is evident that prenatal exposure to low doses of benzodiazepines can result in long-lasting alterations of the cytokine network, as indicated by reduced release of TNF-alpha, IL-1, IL-6, IL-2 and interferon-gamma. The concomitant reduction of peripheral type benzodiazepine receptors on macrophages is discussed as a possible link between prenatal treatment and disturbed function.