Neonatal lead exposure potentiates sickness behavior induced by Listeria monocytogenes infection of mice

Influence of lead-induced toxicity on the inflammatory cytokines

Lead (Pb2+) is a hazardous heavy metal that is pervasive in the human environment as a result of anthropogenic activity, and poses serious health risks, particularly in children. Due to its innumerable unique physical and chemical properties, it has various applications; therefore, it has become a common environmental pollutant. Lead may cause oxidative stress, and accumulating evidence indicates that oxidative stress influences the pathophysiology of lead poisoning, also called plumbism. The immune system is continually exposed to various environmental pathogens and xenobiotics, including heavy metals such as lead, and appears to be one of the most vulnerable targets. After being exposed to lead, cells are subjected to oxidative stress as a result of reactive oxygen species (ROS) production. When the generation and consumption of ROS are out of equilibrium, various cell structures, particularly phospholipids are disrupted leading to lipid peroxidation. Various inflammatory signalling pathways are activated as a consequence, along with reduced disease resistance, inflammation, autoimmunity, sensitization and disruption of the cell-mediated and humoral immune systems. Lead negatively affects the metabolism of cytokines, including the interleukins IL-2, IL-1b, IL-6, IL-4, IL-8, tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN), as well as the expression and functioning of inflammatory enzymes such as cyclooxygenases. However, the cause of toxicity depends on the kind of lead, dosage, route of entry, exposure period, age, host and genetic predisposition.

Unravelling blood-based epigenetic mechanisms: the impact of hsa-miR-146a and histone H3 acetylation in lead-induced inflammation among occupational workers

BACKGROUND

Occupational and environmental exposure to lead (Pb) is a persistent health problem majorly in developing countries and has been implied to cause epigenetic alterations. Its effect on histone post-translational modifications is not explored in human population. MicroRNAs are epigenetic modulators reported to be differentially expressed under Pb exposure. The present study was targeted to find plausible association between the role of hsa-miR-146a and global histone (H3) acetylation in Pb-induced inflammation in occupationally exposed workers.

MATERIALS AND METHODS

A total of 100 occupationally exposed individuals working in different industries were recruited for the study and divided into 2 groups based on the median Pb levels [low Pb group (Pb < 5 μg/dL) and High Pb group (Pb > 5 μg/dL)]. The Pb levels were measured in whole blood using atomic absorption spectrometry to confirm Pb exposure. Histone H3 acetylation and serum interleukin-6 (IL-6) levels were measured using colorimetric methods and enzyme-linked immunosorbent assay (ELISA), respectively. MicroRNA-146a expression was quantified using TaqMan assay.

RESULTS

The median BLL of the study population was 5 μg/dL. BLL, IL-6, and Histone (H3) acetylation increased significantly with the duration of exposure. BLL level showed a significant positive correlation with IL-6 and histone H3 acetylation level. We also found that hsa-miR-146a exhibited significantly increased expression in the high Pb group compared to the low Pb group (Fold change: 2.56; P = 0.014). The linear regression model suggested that BLL has significantly predicted histone H3 acetylation, hsa-miR-146a, and IL-6 in the study subjects.

CONCLUSION

The finding that hsa-miR146a was significantly upregulated in individuals with high BLL and had a significant negative correlation with serum IL-6 suggests that Pb-induced oxidative stress likely activates H3 acetylation, which then releases inflammatory cytokines like IL-6.

Evaluation of the Effect of Pb Pollution on Avian Influenza Virus-Specific Antibody Production in Black-Headed Gulls (Chroicocephalus ridibundus)

Lead (Pb), an environmental pollutant, has been widely reported to have contaminated mammals, including humans and birds. This study focuses on the effects of Pb pollution on avian influenza virus (AIV) antibody production. A total of 170 black-headed gulls (Chroicocephalus ridibundus) were captured in Tokyo Bay (TBP) from January 2019 to April 2020 and in Mikawa Bay (MBP) from November 2019 to April 2021. The gulls were weighed, subjected to blood sampling, and released with a ring band on their tarsus. The samples were used to measure blood Pb levels (BLL) and AIV-specific antibodies. The BLL were compared using the Wilcoxon two-sample test between the period when black-headed gulls arrived and the wintering period, defined by the number of gulls counted in each area. A significant increase was found in the TBP. A decrease in BLL significantly increased antibody titer during wintering in TBP and MBP. Pb pollution had a negative effect on the production of AIV antibodies. These findings suggest that wild birds that were contaminated by Pb in the environment may facilitate the spread of zoonotic diseases, further increasing the possibility that environmental pollutants may threaten human health.

Curcumin and cinnamon mitigates lead acetate-induced oxidative damage in the spleen of rats

Lead toxicity is a common occupational and environmental health hazard that exerts many toxic effects on animals and humans, including immunotoxicity. Curcumin (CUR) and cinnamon (CIN) are common medicinal herbs with immunostimulatory and antioxidant properties. Therefore, this study investigated the protective effect of curcumin and cinnamon against lead acetate (LA)-induced splenotoxicity in rats via hemato-biochemical, immunological, oxidative stress marker, CYP-2E1 expression, histological, and immunohistological evaluations. Four groups of seven rats each were used: the control group received corn oil as a vehicle; the lead acetate group received (100 mg/kg), the CUR + LA group received curcumin (400 mg/kg) plus lead acetate, and the CIN + LA group received cinnamon (200 mg/kg) plus lead acetate orally for 1 month. LA exposure induced macrocytic hypochromic anemia, leukocytosis, neutrophilia, monocytosis, and lymphopenia. Additionally, significant elevations in serum iron, ferritin levels, and transferrin saturation percentage with significant decline of total and unsaturated iron binding capacities (TIBC and UIBC), transferrin, and immunoglobulin G and M levels were recorded. In addition, lead acetate significantly upregulated splenic CYP-2E1 expression, that was evident by significant depletion of reduced glutathione (GSH) activity and elevation of malondihyde (MDA), nitric oxide (NO), and protein carbonyl (PC) concentrations in the spleen. Histologically, hyperplasia of lymphoid follicles, hemosiderin deposition, and disturbance of CD3 and CD68 immuno-expressions were evident in the spleen from the lead acetate group. However, curcumin and cinnamon administration restored the hemato-biochemical, immunological, and oxidative stress parameters as well as histological and immunohistological pictures toward normalcy. In conclusion, curcumin and cinnamon can partially ameliorate LA-induced oxidative damage in the spleen, possibly through their antioxidant, immunomodulatory, and gene-regulating activities.

Effects of clinoptilolite on heavy metal levels in milk, proinflammatory cytokine responses (IL-1β and IL-6) and oxidative stress in dairy cows

The effects of clinoptilolite on milk copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd) and iron (Fe) concentrations, proinflammatory cytokine responses, oxidative stress status, whole blood cell counts and liver and kidney functions were investigated in dairy cows exhibiting no signs of any kind of toxicity. Clinoptilolite was added to the feed at a dose of 200 mg kg-1 body weight in the clinoptilolite-treated group (n = 14), but was not added to the feed in the control group (n = 7). In the milk samples (n = 21) collected before the experiment, the Cu, Pb, Zn, Cd and Fe values were 0.021 ± 0.020, 0.104 ± 0.01, 3.42 ± 0.32, <0.000, 0.56 ± 0.34 ppm, respectively. At the end of the experiment (30th day), among the elements measured in milk samples collected from the clinoptilolite-treated group, only the Pb value (0.076 ± 0.01) was lower than the 0-day value of the clinoptilolite-treated group (0.104 ± 0.01) and the 30th-day value of the control group (0.105 ± 0.01) was found to be statistically lower. Changes determined at the end of clinoptilolite application in serum superoxide dismutase (SOD), malondialdehyde (MDA), albumin, glucose, urea and urine creatinine/urine total protein (uCr/uTP) values, which were interpreted as the effect of lead exposure before the trial, were evaluated as the positive effect of clinoptilolite. It was concluded that the addition of clinoptilolite to the feed in dairy cows caused a significant decrease in the amount of Pb in milk, and positive changes in the parameters related to oxidative stress in serum and in parameters related to renal function.

Potential mechanisms of some selected heavy metals in the induction of inflammation and autoimmunity

Inflammation is a physiological event that protects tissues from infection and injury. Chronic inflammation causes immune cell over activation and sustained release of inflammatory cytokines and chemokines cause pathologic conditions including autoimmune diseases. Heavy metals exposure affects innate and adaptive immune systems through triggering inflammatory responses. It seems that extended inflammatory responses could accelerate heavy metal-induced autoimmunity. In the present review we discuss the exposure route and toxicity of Cadmium (Cd), Lead (Pb), Mercury (Hg), Vanadium (V) and Platinum (Pt) and their effects on inflammatory responses by innate and adaptive immune system and autoimmunity.

Apple phenolic extract ameliorates lead-induced cognitive impairment, depression- and anxiety-like behavior in mice through abating oxidative stress, inflammation and apoptosis via miR-22-3p/SIRT1 axis

Lead can lead to neurotoxicity and cognitive impairment. In this study, for the first time, the protective effects and working mechanisms of apple phenolic extract (APE) against lead acetate (Pb(Ac)2)-induced...

Low concentrations of lead disturb phenotypical markers of the inflammatory and the anti-inflammatory profile of bone marrow-derived macrophages from BALB/c mice

Lead (Pb) is a ubiquitous toxic metal that decreases resistance to infections, in which the macrophages have an essential role. Pb adverse effects on nitric oxide (NO^-) production and variable effects on inflammatory cytokines in activated macrophages have been reported, but no effects have been reported in anti-inflammatory macrophages. We studied Pb (0.03-6 μg/dL equivalent to 0.014-2.89 μM) effects on the function of bone marrow-derived macrophages (BMDM) induced to either inflammatory or anti-inflammatory phenotypes, with LPS + IFNγ or IL-4+IL-13, respectively, and whether these effects are related. Pb did not induce cytotoxicity at any concentration in both macrophage phenotypes. In inflammatory BMDM, Pb (6 μg/dL) inhibited NO^- production without affecting inducible nitric oxide synthase (iNOS) levels or basal arginase activity. At 3 and 6 μg/dL, Pb enhanced the major histocompatibility complex class II (MHC II) membrane expression but did not modify CD86 expression, TNFα, or IL-1β production and secretion. In anti-inflammatory BMDM, Pb did not alter arginase activity, but at 3 and 6 μg/dL, increased TGF-β1 and mannose receptor expression. Results showed that environmentally relevant concentrations of Pb alter functional outcomes or phenotypic markers of anti-inflammatory for the first time. The Pb effects on the inflammatory macrophages are not dependent on negative feedback resulting from the Pb effect on the anti-inflammatory phenotype. The Pb affected only some molecules or specific pathways related to both phenotypes. These effects could be related to Pb effects on immune defense against intracellular pathogens and allergy susceptibility.

Effects of long-term high-level lead exposure on the immune function of workers

This work was undertaken to study the immunomodulatory effects of long-term exposure to varying levels of lead (Pb) in workers. A total of 49 people who underwent occupational health examinations from 2009 to 2018 were selected as study subjects. Differences between the two group populations regarding the levels of T-lymphocytes, B-lymphocytes, natural killer (NK) cells, and granulocytes, as well as the levels of T_H1/T_H2/T_H17 cytokines, were evaluated. The results indicated that the percentages of CD3⁺ cells in the high-Pb group were significantly higher than those in the low-Pb counterparts (p < .05). In contrast, the percentages of CD3^-CD16⁺CD56⁺ cells were significantly lower in the high-Pb workers. There were no significant differences in other immunommy cells and T_H1/T_H2/T_H17 cytokine between the groups. CD3⁺ cell levels in workers positively correlated with blood Pb levels (Rs = 0.378, p = .007), while the expression of CD3^-CD16⁺CD56⁺ cells was negatively correlated (Rs = -0.320, p = .025). There was no significant correlation between blood Pb concentration and the other immune endpoints evaluated here.

The Systemic and Cellular Metabolic Phenotype of Infection and Immune Response to Listeria monocytogenes

It is widely accepted that infection and immune response incur significant metabolic demands, yet the respective demands of specific immune responses to live pathogens have not been well delineated. It is also established that upon activation, metabolic pathways undergo shifts at the cellular level. However, most studies exploring these issues at the systemic or cellular level have utilized pathogen associated molecular patterns (PAMPs) that model sepsis, or model antigens at isolated time points. Thus, the dynamics of pathogenesis and immune response to a live infection remain largely undocumented. To better quantitate the metabolic demands induced by infection, we utilized a live pathogenic infection model. Mice infected with Listeria monocytogenes were monitored longitudinally over the course of infection through clearance. We measured systemic metabolic phenotype, bacterial load, innate and adaptive immune responses, and cellular metabolic pathways. To further delineate the role of adaptive immunity in the metabolic phenotype, we utilized two doses of bacteria, one that induced both sickness behavior and protective (T cell mediated) immunity, and the other protective immunity alone. We determined that the greatest impact to systemic metabolism occurred during the early immune response, which coincided with the greatest shift in innate cellular metabolism. In contrast, during the time of maximal T cell expansion, systemic metabolism returned to resting state. Taken together, our findings demonstrate that the timing of maximal metabolic demand overlaps with the innate immune response and that when the adaptive response is maximal, the host has returned to relative metabolic homeostasis.

Antioxidant, anti-inflammatory and anti-apoptotic effects of hydro-ethanolic extract of Cyperus esculentus L. (tigernut) on lead acetate-induced testicular dysfunction in Wistar rats

AIM

Lead acetate impairs testicular function by enhancing testicular oxidative stress and apoptosis. Cyperus esculentus possesses antioxidants and has shown great improvement of testicular function. This study investigated the protective effect of hydro-ethanolic extract of Cyperus esculentus on lead acetate-induced testicular dysfunction in Wistar rats.

MATERIALS AND METHODS

Twenty-five male Wistar rats (180-195 g) were randomly divided into 5 groups (n = 5) namely: Normal control (NC), Lead control (PbC) (20 mg/kg b.w. i.p.), C. esculentus-treated (CE) (500 mg/kg b.w p.o.), Pb + CE(500) (20 mg/kg of lead and 500 mg/kg of extract) and Pb + CE(1000) (20 mg/kg of lead and 1000 mg/kg of extract). Administration lasted for 21 days.

RESULTS

Sperm count, motility, viability, serum testosterone and follicle stimulating hormone, Johnsen's score, Leydig cell count, Sertoli cell count, testicular testosterone, B-cell lymphoma protein-2 (Bcl-2), steroidogenic acute regulatory protein, cytochrome P450 A1, 3β-hydroxysteroid dehydrogenase (HSD), 17β-HSD, enzymatic antioxidant activities and total antioxidant capacity were significantly (p < 0.05) decreased in PbC compared with NC. These parameters however increased significantly (p < 0.05) in Pb + CE(500) and Pb + CE(1000) compared with PbC. Lead acetate upregulated (p < 0.05) testicular malondialdehyde, nitric oxide, glucose, lactate, lactate dehydrogenase, C-reactive protein, tumor necrosis factor-α, interleukin (IL)-6, IL-1β, Bcl-2 associated X (Bax), Bax/Bcl-2 and cleaved caspase-3 levels. All these parameters were downregulated (p < 0.05) in Pb + CE(500) and Pb + CE(1000) in comparison with PbC.

CONCLUSION

C. esculentus exhibited a dose-dependent mitigation of lead acetate-induced testicular dysfunction in Wistar rats via its antioxidant, anti-inflammatory and anti-apoptotic effects.

Evaluating the effects between metal mixtures and serum vaccine antibody concentrations in children: a prospective birth cohort study

BACKGROUND

Many populations are exposed to arsenic, lead, and manganese. These metals influence immune function. We evaluated the association between exposure to single and multiple metals, including arsenic, lead, and manganese, to humoral immunity as measured by antibody concentrations to diphtheria and tetanus toxoid among vaccinated Bangladeshi children. Additionally, we examined if this association was potentially mediated by nutritional status.

METHODS

Antibody concentrations to diphtheria and tetanus were measured in children's serum at age 5 (n = 502). Household drinking water was sampled to quantify arsenic (W-As) and manganese (W-Mn), whereas lead was measured in blood (B-Pb). Exposure samples were taken during pregnancy, toddlerhood, and early childhood. Multiple linear regression models (MLRs) with single or combined metal predictors were used to determine the association with antibody outcomes. MLR results were transformed to units of percent change in outcome per doubling of exposure to improve interpretability. Structural equation models (SEMs) were used to further assess exposure to metal mixtures. SEMs regressed a latent exposure variable (Metals), informed by all measured metal variables (W-As, W-Mn, and B-Pb), on a latent outcome variable (Antibody), informed by measured antibody variables (diphtheria and tetanus). Weight-for-age z-score (WFA) at age 5 was evaluated as a mediator.

RESULTS

Diphtheria antibody was negatively associated with W-As during pregnancy in MLR, but associations were attenuated after adjusting for W-Mn and B-Pb (- 2.9% change in diphtheria antibody per doubling in W-As, 95% confidence interval [CI]: - 7%, 1.5%). Conversely, pregnancy levels of B-Pb were positively associated with tetanus antibody, even after adjusting for W-As and W-Mn (13.3%, 95% CI: 1.7%, 26.3%). Overall, null associations were observed between W-Mn and antibody outcomes. Analysis by SEMs showed that the latent Metals mixture was significantly associated with the latent Antibody outcome (β = - 0.16, 95% CI: - 0.26, - 0.05), but the Metals variable was characterized by positive and negative loadings of W-As and B-Pb, respectively. Sex-stratified MLR and SEM analyses showed W-As and B-Pb associations were exclusive to females. Mediation by WFA was null, indicating Metals only had direct effects on Antibody.

CONCLUSIONS

We observed significant modulation of vaccine antibody concentrations among children with pregnancy and early life exposures to drinking water arsenic and blood lead. We found distinct differences by child sex, as only females were susceptible to metal-related modulations in antibody levels. Weight-for-age, a nutritional status proxy, did not mediate the association between the metal mixture and vaccine antibody.

Leukocyte apoptosis, TNF-α concentration and oxidative damage in lead-exposed workers

Lead intoxication can generate pro-inflammatory conditions that have been proposed to be associated with cell injuries and oxidative stress. The pro-inflammatory state can participate in the pathophysiology of this toxicity to generate immune response dysfunctions, which could condition the presence of clinical manifestations and susceptibility to infections already described in lead-exposed patients. In the present work, we study workers of a battery recycler factory (n = 24) who are chronically exposed to lead and compared them with non-lead exposed workers (n = 17). Lead-exposed workers had high lead concentrations in blood (med 69.8 vs. 1.7 μg/dL), low δ-ALAD activity (med 149 vs. 1100 nmol PBG/h/mL), high lipid peroxidation (med 0.86 vs. 0.69 nmol/mL) and high erythrocytes apoptosis (med 0.81 vs. 0.50% PS externalization) in relation to non-lead exposed workers. Also, lead-exposed workers had a high incidence of signs and symptoms related to lead intoxication and a higher frequency of infections. The higher leukocyte apoptosis (med 18.3 vs. 8.2% PS externalization) and lower basal TNF-α concentration (med 0.38 vs. 0.94 pg/mL) in lead-exposed workers imply an immune response dysfunction; however, there was no difference in the TNF-α concentration when leukocytes were stimulated with lipopolysaccharide in whole blood (med 44 vs. 70 pg/mL), suggesting that lead-exposed workers might develop adaptation mechanisms to reduce basal TNF-α release through downregulation processes proposed for this cytokine.

Listeriosis Outbreak in South Africa: A Comparative Analysis with Previously Reported Cases Worldwide

Listeria species are Gram-positive, rod-shaped, facultative anaerobic bacteria, which do not produce endospores. The genus, Listeria, currently comprises 17 characterised species of which only two (L. monocytogenes and L. ivanovii) are known to be pathogenic to humans. Food products and related processing environments are commonly contaminated with pathogenic species. Outbreaks and sporadic cases of human infections resulted in considerable economic loss. South Africa witnessed the world's largest listeriosis outbreak, characterised by a progressive increase in cases of the disease from January 2017 to July 2018. Of the 1060 laboratory-confirmed cases of listeriosis reported by the National Institute of Communicable Diseases (NICD), 216 deaths were recorded. Epidemiological investigations indicated that ready-to-eat processed meat products from a food production facility contaminated with L. monocytogenes was responsible for the outbreak. Multilocus sequence typing (MLST) revealed that a large proportion (91%) of the isolates from patients were sequence type 6 (ST6). Recent studies revealed a recurrent occurrence of small outbreaks of listeriosis with more severe side-effects in humans. This review provides a comparative analysis of a recently reported and most severe outbreak of listeriosis in South Africa, with those previously encountered in other countries worldwide. The review focuses on the transmission of the pathogen, clinical symptoms of the disease and its pathogenicity. The review also focuses on the major outbreaks of listeriosis reported in different parts of the world, sources of contamination, morbidity, and mortality rates as well as cost implications. Based on data generated during the outbreak of the disease in South Africa, listeriosis was added to the South African list of mandatory notifiable medical conditions. Surveillance systems were strengthened in the South African food chain in order to assist in preventing and facilitating early detection of both sporadic cases and outbreaks of infections caused by these pathogens in humans.

Elevated levels of lead exposure and impact on the anti-inflammatory ability of oral sialic acids among preschool children in e-waste areas

The oral health of preschool children in an electronic waste (e-waste) area is susceptible to lead (Pb) exposure increasing the risk of dental caries and causing periodontitis and other oral diseases. The aim of the present study is to investigate the relationship between chronic exposure to Pb and oral anti-inflammatory potential of preschool children. For this analysis, 574 preschool children from 2.5 to 6 years of age were recruited between November and December 2017, in which 357 preschool children were from Guiyu (n = 357), an e-waste-contaminated town, and 217 from Haojiang Shantou. We measured the levels of child blood Pb, salivary sialic acid, serum interleukin-6 (IL-6) and serum tumor necrosis factor-α (TNF-α), and investigated the prevalence of dental caries in deciduous teeth. The medians of blood Pb levels, serum IL-6 and TNF-α were significantly higher in the Guiyu children than in Haojiang children. Concomitantly, salivary sialic acids were lower in the Guiyu children [9.58 (3.97, 18.42) mg/dL] than in Haojiang [17.57 (5.95, 24.23) mg/dL]. Additionally, the prevalence of dental caries in deciduous teeth was significantly higher in the Guiyu children than in Haojiang (62.5% vs. 53.9%). Blood Pb levels were negatively correlated with salivary sialic acids, in which IL-6 played as a mediator of the association between blood Pb levels and saliva sialic acid concentrations according to the mediation model. To our knowledge, this is the first report on the potential association between chronic Pb exposure and the anti-inflammatory ability of oral sialic acids among preschool children. These results suggest that the chronic Pb exposure can reduce salivary sialic acid levels, attenuate oral anti-inflammatory potential and increase the potential risk of dental caries in deciduous teeth among preschool children in an e-waste site.

Lead (Pb) Exposure Enhances Expression of Factors Associated with Inflammation

The human immune system is constantly exposed to xenobiotics and pathogens from the environment. Although the mechanisms underlying their influence have already been at least partially recognized, the effects of some factors, such as lead (Pb), still need to be clarified. The results of many studies indicate that Pb has a negative effect on the immune system, and in our review, we summarize the most recent evidence that Pb can promote inflammatory response. We also discuss possible molecular and biochemical mechanisms of its proinflammatory action, including the influence of Pb on cytokine metabolism (interleukins IL-2, IL-4, IL-8, IL-1b, IL-6), interferon gamma (IFNγ), and tumor necrosis factor alpha (TNF-α); the activity and expression of enzymes involved in the inflammatory process (cyclooxygenases); and the effect on selected acute phase proteins: C-reactive protein (CRP), haptoglobin, and ceruloplasmin. We also discuss the influence of Pb on the immune system cells (T and B lymphocytes, macrophages, Langerhans cells) and the secretion of IgA, IgE, IgG, histamine, and endothelin.

Alteration of the number and percentage of innate immune cells in preschool children from an e-waste recycling area

Heavy metal lead (Pb) and cadmium (Cd) are widespread environmental contaminants and exert detrimental effects on the immune system. We evaluated the association between Pb/Cd exposures and innate immune cells in children from an electronic waste (e-waste) recycling area. A total number of 294 preschool children were recruited, including 153 children from Guiyu (e-waste exposed group), and 141 from Haojiang (reference group). Pb and Cd levels in peripheral blood were measured by graphite furnace atomic absorption spectrophotometer, NK cell percentages were detected by flow cytometer, and other innate immune cells including monocytes, eosinophils, neutrophils and basophils were immediately measured by automated hematology analyzer. Results showed children in Guiyu had significantly higher Pb and Cd levels than in reference group. Absolute counts of monocytes, eosinophils, neutrophils and basophils, as well as percentages of eosinophils and neutrophils were significantly higher in the Guiyu group. In contrast, NK cell percentages were significantly lower in Guiyu group. Pb elicited significant escalation in counts of monocytes, eosinophils and basophils, as well as percentages of monocytes, but decline in percentages of neutrophils in different quintiles with respect to the first quintile of Pb concentrations. Cd induced significant increase in counts and percentages of neutrophils in the highest quintile compared with the first quintile of Cd concentrations. We concluded alteration of the number and percentage of innate immune cells are linked to higher levels of Pb and Cd, which indicates Pb and Cd exposures might affect the innate and adaptive immune response in Guiyu children.

Lead ions abrogate lipopolysaccharide-induced nitric monoxide toxicity by reducing the expression of STAT1 and iNOS

Lead is a widespread environmental pollutant and the highly poisonous metal compromises multiple organs in the body. Among other tissues and cells, lead ions (Pb(2+)) can affect macrophages and microglia cells. The present study observed a concentration-dependent protection of BV-2 microglia and RAW 264.7 macrophages by Pb(2+) against lipopolysaccharide (LPS)-induced toxicity. Both cell lines are potent producers of two substances that have previously been shown to mediate cytotoxic effects of LPS. These are the pro-inflammatory cytokine tumor necrosis factor (TNF)-α and nitric monoxide (NO), which creates nitrosative stress, hampering the distribution of invading pathogens and tumor cells. While the expression of TNF-α was unaffected by Pb(2+), the production of NO was significantly inhibited. Moreover, blocking NO synthesis by low molecular weight inhibitors prevented LPS-mediated toxicity, confirming the role of NO in these events. Pb(2+) exposure led to a downregulation of LPS-induced expression of the transcription factor STAT1, which is involved in iNOS transcription. Moreover, iNOS mRNA and protein levels were reduced in the presence of Pb(2+), explaining the reduced formation of NO and a subsequent increase of cellular viability in vitro. In vivo, the effect might limit collateral damage caused by excessive NO production, but also impair the efficiency of NO as a central mediator of the defense against various pathogens.

Elevated lead levels and adverse effects on natural killer cells in children from an electronic waste recycling area

Lead (Pb) has been proved to exert immunotoxicity to influence immune homeostasis in humans. To monitor the internal Pb level and evaluate its effect on natural killer (NK) cells and cytokine/chemokine concentrations, we recruited 285 preschool children from Guiyu, one of the largest electronic waste (e-waste) destinations and recycling areas in the world, and known to have high concentrations of Pb in the air, soil, water, sediment and plants. A total of 126 preschool children were selected from Haojiang as a reference group. Results showed that children in Guiyu, the exposed area, had higher blood Pb levels and lower percentages of NK cells than children from the reference area. A significantly negative association was found between the percentage of NK cells and increasing Pb levels. Moreover, children in Guiyu area had higher platelet counts and IL-1β concentrations, and lower levels of IL-2, IL-27, MIP-1α and MIP-1β were observed in the exposed children. These changes might not be conducive to the development and differentiation of NK cells. Taken together, the elevated Pb levels result in the lower percentages of NK cells, but also alter the levels of platelets, IL-1β and IL-27, which might be unconducive to the activity and function of NK cells.

Metallothionein differentially affects the host response to Listeria infection both with and without an additional stress from cold-restraint

Acute stress alters anti-bacterial defenses, but the neuroimmunological mechanisms underlying this association are not yet well understood. Metallothionein (MT), a cysteine-rich protein, is a stress response protein that is induced by a variety of chemical, biological, and psychological stressors, and MT has been shown to influence immune activities. We investigated MT's role in the management of anti-bacterial responses that occur during stress, using a C57BL/6 (B6) strain that has targeted disruptions of the Mt1 and Mt2 genes (B6-MTKO), and a B6 strain that has additional copies of Mt (B6-MTTGN). The well-characterized listeriosis model was used to examine immune mechanisms that are altered by a 1-h stress treatment (cold-restraint, CR) administered just prior to bacterial infection. Intriguingly, MT gene doses both greater and lower than that of wild-type (WT) B6 mice were associated with improved host defenses against Listeria monocytogenes (LM). This augmented protection was diminished by CR stress in the MTKO mice, but transgenic mice with additional MT copies had no CR stress-induced increase in their listerial burden. During the transition from innate to adaptive immunity, on day 3 after infection, oxidative burst and apoptosis were assessed by flow cytometric methods, and cytokine transcription was measured by real-time quantitative PCR. MT gene expression and CR-stress affected the expression of IL-6 and TNFα. Additionally, these genetic and environmental modulations altered the generation of ROS responses as well as the number of apoptotic cells in livers and spleens. Although the level of MT altered the listerial response, MT expression was equally elevated by listerial infection with or without CR stress. These results indicate the ability of MT to regulate immune response mechanisms and demonstrate that increased amounts of MT can eliminate the immunosuppression induced by CR.

Multigenerational epigenetic inheritance in humans: DNA methylation changes associated with maternal exposure to lead can be transmitted to the grandchildren

We report that the DNA methylation profile of a child’s neonatal whole blood can be significantly influenced by his or her mother’s neonatal blood lead levels (BLL). We recruited 35 mother-infant pairs in Detroit and measured the whole blood lead (Pb) levels and DNA methylation levels at over 450,000 loci from current blood and neonatal blood from both the mother and the child. We found that mothers with high neonatal BLL correlate with altered DNA methylation at 564 loci in their children’s neonatal blood. Our results suggest that Pb exposure during pregnancy affects the DNA methylation status of the fetal germ cells, which leads to altered DNA methylation in grandchildren’s neonatal dried blood spots. This is the first demonstration that an environmental exposure in pregnant mothers can have an epigenetic effect on the DNA methylation pattern in the grandchildren.

A physical/psychological and biological stress combine to enhance endoplasmic reticulum stress

The generation of an immune response against infectious and other foreign agents is substantially modified by allostatic load, which is increased with chemical, physical and/or psychological stressors. The physical/psychological stress from cold-restraint (CR) inhibits host defense against Listeria monocytogenes (LM), due to early effects of the catecholamine norepinephrine (NE) from sympathetic nerves on β1-adrenoceptors (β1AR) of immune cells. Although CR activates innate immunity within 2h, host defenses against bacterial growth are suppressed 2-3 days after infection (Cao and Lawrence 2002). CR enhances inducible nitric oxide synthase (iNOS) expression and NO production. The early innate activation leads to cellular reduction-oxidation (redox) changes of immune cells. Lymphocytes from CR-treated mice express fewer surface thiols. Splenic and hepatic immune cells also have fewer proteins with free thiols after CR and/or LM, and macrophages have less glutathione after the in vivo CR exposure or exposure to NE in vitro. The early induction of CR-induced oxidative stress elevates endoplasmic reticulum (ER) stress, which could interfere with keeping phagocytized LM within the phagosome or re-encapsuling LM by autophagy once they escape from the phagosome. ER stress-related proteins, such as glucose-regulated protein 78 (GRP78), have elevated expression with CR and LM. The results indicate that CR enhances the unfolded protein response (UPR), which interferes with host defenses against LM. Thus, it is postulated that increased stress, as exists with living conditions at low socioeconomic conditions, can lower host defenses against pathogens because of oxidative and ER stress processes.

Function of respiratory system evaluated using selected spirometry parameters in persons occupationally exposed to lead without evident health problems

This study aimed at evaluation of selected spirometric parameters in persons occupationally exposed to lead without evident health problems. The studies were conducted on 69 men occupationally exposed to lead. Occupational exposure to lead was characterized by estimation of blood lead concentration (Pb-B) and blood zinc protoporphyrin concentration (ZnPP). Function of respiratory system was examined using spirometric analysis with evaluation of its basic parameters: forced vital capacity (FVC), forced expiratory volume (in 1s) (FEV1), Tiffeneau index (FEV1%VC) and peak expiratory flow (PEF). In the study group negative linear correlations were documented between Pb-B and FVC, FEV 1 and FEV1%VC. A more pronounced age, higher values of BMI and higher blood lead concentration constituted independent risk factors for reduced FEV1%VC.

CONCLUSION

Persons occupationally exposed to lead with elevated blood lead concentration and blood zinc protoporphyrin concentration manifested the impaired function of respiratory system, evaluated using parameters of spirometry.

Cross-species coherence in effects and modes of action in support of causality determinations in the U.S. Environmental Protection Agency's Integrated Science Assessment for Lead

The peer-reviewed literature on the health and ecological effects of lead (Pb) indicates common effects and underlying modes of action across multiple organisms for several endpoints. Based on such observations, the United States (U.S.) Environmental Protection Agency (EPA) applied a cross-species approach in the 2013 Integrated Science Assessment (ISA) for Lead for evaluating the causality of relationships between Pb exposure and specific endpoints that are shared by humans, laboratory animals, and ecological receptors (i.e., hematological effects, reproductive and developmental effects, and nervous system effects). Other effects of Pb (i.e., cardiovascular, renal, and inflammatory responses) are less commonly assessed in aquatic and terrestrial wildlife limiting the application of cross-species comparisons. Determinations of causality in ISAs are guided by a framework for classifying the weight of evidence across scientific disciplines and across related effects by considering aspects such as biological plausibility and coherence. As illustrated for effects of Pb where evidence across species exists, the integration of coherent effects and common underlying modes of action can serve as a means to substantiate conclusions regarding the causal nature of the health and ecological effects of environmental toxicants.

Lead modulation of macrophages causes multiorgan detrimental health effects

The environmental toxicant lead (Pb) has detrimental effects on a number of organ systems, including the immune system. Pb exposure decreases host immune defenses against numerous microorganisms and cancer. Although Pb effects on humoral and cell-mediated immunity as well as on erythrocyte, neural, and renal pathophysiology have been well documented, there are few reports regarding Pb's impact on innate immunity, which can affect multiorgan processes. This review focuses on Pb modulation of a key innate immune cell, the macrophage. The impact of Pb on macrophages in different organs, on immature versus mature macrophages, and on low versus high Pb concentrations is discussed. Pb decreases phagocytosis and chemotaxis of macrophages and affects nitric oxide production and eicosanoid metabolism in mature macrophages. Pretreatment of macrophages with Pb increases TNF-α secretion after in vitro stimulation with lipopolysaccharide; however, Pb exposure decreases in vivo intracellular pathogen killing. More recent evidence from mouse studies indicates that even low, environmentally relevant, blood concentrations of Pb result in increased phagocytosis of erythrocytes and decreased expression of interferon-gamma-inducible GTPases, p65-GBP, and p47-IRG, which are necessary for intracellular pathogen killing. Taking into account the effects of Pb on macrophages, the review describes posited mechanisms to account for Pb-altered health effects; Pb effects on heme levels may play a key role as well as Pb's preferential induction of helper type-2 T (Th2) cells and M2 macrophages, which is related to oxidative stress. The discussion links old findings with new, thereby adding new insight into the effects of Pb on macrophages and the resultant compromised immunity and health.

Developmental lead effects on behavior and brain gene expression in male and female BALB/cAnNTac mice

Lead (Pb) was one of the first poisons identified, and the developing nervous system is particularly vulnerable to its toxic effects. Relatively low, subclinical doses, of Pb that produce no overt signs of encephalopathy can affect cognitive, emotional, and motor functions. In the present study, the effects of developmental Pb-exposure on behavioral performance and gene expression in BALB/cAnNTac mice were evaluated. Pups were exposed to Pb from gestational-day (gd) 8 to postnatal-day (pnd) 21 and later evaluated in exploratory behavior, rotarod, Morris water maze, and resident-intruder assays as adults. Pb-exposure caused significant alterations in exploratory behavior and water maze performance during the probe trial, but rotarod performance was not affected. Pb-exposed males displayed violent behavior towards their cage mates, but not to a stranger in the resident-intruder assay. Gene expression analysis at pnd21 by microarray and qRT-PCR was performed to provide a molecular link to the behavior changes that were observed. Pb strongly up-regulated gene expression within the signaling pathways of mitogen activated protein kinases (MAPKs), extra-cellular matrix (ECM) receptor, focal adhesion, and vascular endothelial growth-factor (VEGF), but Pb down-regulated gene expression within the pathways for glycan structures-biosynthesis 1, purine metabolism, and N-glycan biosynthesis. Pb increased transcription of genes for major histocompatibility (MHC) proteins, the chemokine Ccl28, chemokine receptors, IL-7, IL7R, and proteases. The qRT-PCR analysis indicated an increase of gene expression in the whole brain for caspase 1 and NOS2. Analysis of IL-1β, caspase 1, NOS2, Trail, IL-18 and IL-33 gene expression of brain regions indicated that Pb perturbed the inter-regional expression pattern of pro-inflammatory genes. Brain region protein concentrations for IL-10, an anti-inflammatory cytokine, showed a significant decrease only within the cortex region. Results indicate that Pb differentially affects the behavior of male and female mice in that females did less exploration and the males were selectively more aggressive. Gene expression data pointed to evidence of neuroinflammation in the brain of both female and male mice. Pb had more of an effect in the males on expression of vomeronasal receptor genes associated with odor detection and social behavior.

Assessment of immunotoxicity parameters in individuals occupationally exposed to lead

Although adverse health effects produced by lead (Pb) have long been recognized, studies regarding the immunotoxic effects of occupational exposure report conflicting results. In a previous study, alterations in some immunological parameters were noted in 70 Pb-exposed workers. In view of these results, it was of interest to extend this study comprising a larger population and increasing the number of immunological endpoints assessed. Accordingly, in this study the immunotoxic effects of occupational exposure to Pb were assessed by analyzing (1) percentages of lymphocyte subsets (CD3⁺, CD4⁺, CD8⁺, CD19⁺, and CD56⁺/16⁺); (2) concentration of plasma cytokines, namely, interleukin (IL) 2, IL4, IL6, IL10, tumor necrosis factor (TNF) α, and interferon (IFN) γ; and (3) plasma concentrations of neopterin, tryptophan (Trp), and kynurenine (Kyn). In addition, the possible influence of genetic polymorphisms in the vitamin D receptor (VDR) and δ-aminolevulinic acid dehydratase (ALAD) genes on immunotoxicity parameters was studied. Exposed workers showed significant decreases in %CD3⁺, %CD4⁺/%CD8⁺ ratio, IL4, TNFα, IFNγ, and Kyn to Trp ratio (Kyn/Trp), and significant increases in %CD8⁺, IL10, and Trp levels. All these parameters, except Trp, were significantly correlated with exposure biomarkers. No significant influence of genetic polymorphisms was observed. Significant correlation between Kyn/Trp and neopterin concentrations suggests an involvement of indoleamine 2,3-dioxygenase in the Trp metabolic alterations, which may contribute to some of the immune alterations observed. Results obtained suggest that occupational exposure to PB may influence the immune system by impairing several mechanisms, which might ultimately produce deregulation of the immune response and diminish immunosurveillance in exposed individuals.

Central nervous system cytokine gene expression: modulation by lead

The environmental heavy metal toxicant, lead (Pb) has been shown to be more harmful to the central nervous system (CNS) of children than to adults, given that Pb exposure affects the neural system during development. Because growth factors and cytokines play very important roles in development of the CNS, we have examined the impact of Pb exposure on the expression of cytokines during CNS development. Cytokine expression was studied in post-natal-day 21 (pnd21) mice by microarray, real-time RT-PCR, Luminex, and ELISA methodologies. BALB/c mouse pups were exposed to Pb through the dam's drinking water (0.1 mM Pb acetate), from gestation-day 8 (gd8) to pnd21. Two cytokines, interleukin-6 (IL-6) and transforming growth factor-β1 (TGF-β1), displayed significantly changed transcript levels in the presence of Pb. IL-6 and TGF-β1 both have signal transduction cascades that can cooperatively turn on the gene for the astrocyte marker glial-fibrillary acidic protein (GFAP). Microarray results indicated that Pb exposure significantly increased expression of GFAP. Pb also modulated IL-6, TGF-β1, and IL-18 protein expression in select brain regions. The deleterious effects of Pb on learning and long-term memory are posited to result from excessive astrocyte growth and/or activation with concomitant interference with neural connections. Differential neural expression of cytokines in brain regions needs to be further investigated to mechanistically associate Pb and neuroinflammation with behavioral and cognitive changes.

Ubiquitous hazardous metal lead induces TNF-α in human phagocytic THP-1 cells: primary role of ERK 1/2

Induction of tumor necrosis factor-α (TNF-α) in response to lead (Pb) exposure has been implicated in its immunotoxicity. However, the molecular mechanism by which Pb upregulates the level of TNF-α is wagely known. An attempt was therefore made to elucidate the mechanistic aspect of TNF-α induction, mainly focusing transcriptional and post transcriptional regulation via mitogen activated protein kinases (MAPKs) activation. We observed that exposure of Pb to human monocytic THP-1 cells resulted in significant enhanced production of TNF-α m-RNA and protein secretion. Moreover, the stability of TNF-α m-RNA was also increased as indicated by its half life. Notably, activation of ERK 1/2, p38 and JNK in Pb exposed THP-1 was also evident. Specific inhibitor of ERK1/2, PD 98059 caused significant inhibition in production and stability of TNF-α m-RNA. However, SB 203580 partially inhibited production and stability of TNF-α m-RNA. Interestingly, a combined exposure of these two inhibitors completely blocked modulation of TNF-α m-RNA. Data tends to suggest that expression and stability of TNF-α induction due to Pb exposure is mainly regulated through ERK. Briefly, these observations are useful in understanding some mechanistic aspects of proinflammatory and immunotoxicity of Pb, a globally acknowledged key environmental contaminant.

Lymphocyte subpopulations in human exposure to metals (IUPAC Technical Report)

Numerous species of metal ions cause immunosensitization in humans. Possible approaches to determine those occupational and environmental exposures to metals that result in immunological changes include lymphocyte transformation assay, cytokine profiling, and measurement of lymphocyte subpopulations. In two previous papers, we considered lymphocyte transformation assay [1] and cytokine profiling [2]. Here we review the effects of exposures to metals on lymphocyte subpopulations. Specific consideration is given to beryllium, chromium, cobalt, nickel, palladium and platinum, cadmium, gold, mercury, and lead. Analysis of the scientific literature shows that immunosensitizing metals may have influences on the lymphocyte subset composition, but only in a few instances does exposure to metals cause reproducible shifts of lymphocyte subpopulations. If lymphocyte subpopulations are analyzed, each diagnostic step, including indication, sample handling, analytic procedure, and data interpretation, should adhere to good quality assurance and quality control.

Interactions among infections, nutrients and xenobiotics

During recent years there have been several incidents in which symptoms of disease have been linked to consumption of food contaminated by chemical substances (e.g., 2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD). Furthermore, outbreaks of infections in food-producing animals have attracted major attention regarding the safety of consumers, e.g., Bovine Spongiform Encephalitis (BSE) and influenza in chicken. As shown for several xenobiotics in an increasing number of experimental studies, even low-dose xenobiotic exposure may impair immune function over time, as well as microorganism virulence, resulting in more severe infectious diseases and associated complications. Moreover, during ongoing infection, xenobiotic uptake and distribution are often changed resulting in increased toxic insult to the host. The interactions among infectious agents, nutrients, and xenobiotics have thus become a developing concern and new avenue of research in food toxicology as well as in food-borne diseases. From a health perspective, in the risk assessment of xenobiotics in our food and environment, synergistic effects among microorganisms, nutrients, and xenobiotics will have to be considered. Otherwise, such effects may gradually change the disease panorama in society.

Diagnostic relevance of the determination of lymphocyte subpopulations in environmental medicine

Earlier hopes that determination of lymphocyte subpopulations might become a strong diagnostic tool in environmental medicine have not been fulfilled in recent years. Analysis of the scientific literature rather shows that there are only few examples for environmental exposures causing reproducible shifts of lymphocyte subpopulations. Moreover, current knowledge suggests that "environmental diseases" are not associated with characteristic changes of subpopulation patterns. If lymphocyte subpopulations are analyzed, each diagnostic step, including indication, sample handling, analytic procedure and data-interpretation, should adhere to good quality criteria. Taking all together, the determination of lymphocyte subpopulations in the context of environmental medicine comes under category IV of the criteria of the Commission for Methods and Quality Assurance in Environmental Medicine of the German federal health authority (Robert Koch-Institute; RKI): "A procedure cannot be recommended because there is not sufficient information to justify it" (here: no solid trends in epidemiological examinations), "and because theoretical considerations speak against an application" (here: high physiological variability and missing exposure or substance specificity).

Lead and immune function

The heavy metal lead is a widely deposited environmental toxicant known to impact numerous physiological systems, including the reproductive, neurological, hepatic, renal, and immune systems. Studies illustrating the capacity of lead to impair immune function and/or host resistance to disease date back to at least the 1960s. However, it has only been in recent years that lead has been recognized among a new category of immunotoxicants-those that dramatically shift immune functional capacity while producing only modest changes to immune cell populations and lymphoid organs. These relatively noncytotoxic immunomodulating chemicals and drugs represent the immunotoxic hazards most difficult to identify and problematic for risk assessment using historic approaches. As a result, such environmental factors are also among the most likely to contribute to chronic immune-related disease at relevant exposure levels. This review considers the animal and human evidence that lead exposure can produce a stark shift in immune functional capacity with a skewing predicted to elevate the risk of atopic and certain autoimmune diseases. At the same time, host defenses against infectious agents and cancer may be reduced. Age-based exposure studies also suggest that levels of blood lead previously thought to be safe, that is, below 10 microg/dl, may be associated with later life immune alterations.

Host resistance model to an intracellular pathogen

This unit describes a model for the determination of host resistance in mice using a Gram-positive intracellular bacterium, Listeria monocytogenes (LM), and discusses its broad use in immunotoxicological studies. The provides detailed procedures for LM infection and sample analysis, including preparation and infection of mice with LM, recording of sickness behaviors in infected mice, and determination of viable LM numbers in the tissues from infected animals. The protocol also describes use of serum and tissue homogenates for assessment of cytokines. Additionally, background information on LM and LM infection is provided for better understanding and utilization of this model. The LM infection model is useful for the initial screening of possible modulation of immune responses, particularly innate immunity and type-1 cell-mediated immunity (CMI), by environmental factors, as well as for further investigation of the underlying mechanisms of environmental factor-induced changes in immunity.

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.

COEXPOSURE OF LEAD- AND LIPOPOLYSACCHARIDE-INDUCED LIVER INJURY IN RATS: INVOLVEMENT OF NITRIC OXIDE-INITIATED OXIDATIVE STRESS AND TNF-??

In this study, we investigated the interaction between lipopolysaccharide (LPS) and lead (Pb) and the involvement of tumor necrosis factor-alpha (TNF-alpha) and oxidative stress in Pb-plus-LPS (Pb/LPS)-induced liver damage in rats. Serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), TNF-alpha, nitric oxide (NO), and lipid peroxidation (LPO) were determined in rats treated with Pb and/or LPS. Pb ranging from 0 to 15 mg/kg dose dependently increased AST, ALT, NO, or LPO in LPS-treated rats. Pretreatment with iNOS inhibitor 1400W reduced NO, LPO, TNF-alpha, AST, and ALT in Pb/LPS-treated rats. Thus, Pb increased LPS-induced liver damage, which might be associated with increased NO-initiated oxidative stress and TNF-alpha in rats.

Lead-induced changes in human erythrocytes and lymphocytes

In the present work we studied, by chemiluminescence measurements, the influence of lead on the production of reactive oxygen species (ROS) in haemolysates obtained from human erythrocytes incubated in the presence of different concentrations of lead acetate. Moreover, we evaluated the modification of proteins and lipids in human erythrocyte and lymphocyte membranes by using the fluorescence probes N-(1-pyrene)maleimide (PM), laurdan and pyrene. No significant changes in chemiluminescence were detected for erythrocytes incubated with 1-10 microM lead acetate for 3 h at 37 degrees C. By increasing the lead acetate concentration in cell suspensions up to 50 microM for the same incubation time, the percentage of chemiluminescence inhibition was ca. 20%. It was shown that, after incorporating fluorescence probes in the membrane lipid bilayer of erythrocytes and lymphocytes treated with 10 and/or 50 microM lead acetate, the total fluorescence intensity and the excimer to monomer intensity ratio of PM decreased and the generalized fluorescence polarization of laurdan decreased by 10-15%. The pyrene excimerization coefficient (kappa(ex)) increased by 20% (in comparison with a magnitude of kappa(ex) for white membranes isolated from intact erythrocytes) with 6-10 microM lead acetate for 3 h at 37 degrees C. The data obtained suggest that the effect of low concentrations of lead acetate does not cause production of ROS in erythrocytes in vitro, but can change the physicochemical state of proteins and lipids in erythrocyte and lymphocyte membranes. This effect is important because it influences the enzymatic activity and the functionality of receptors and channels present at the plasma membrane level, thus modulating the molecular composition of the intracellular space and cell functions.

Developmental immunotoxicology of lead

The heavy metal, lead, is a known developmental immunotoxicant that has been shown to produce immune alterations in humans as well as other species. Unlike many compounds that exert adverse immune effects, lead exposure at low to moderate levels does not produce widespread loss of immune cells. In contrast, changes resulting from lead exposure are subtle at the immune cell population level but, nevertheless, can be functionally dramatic. A hallmark of lead-induced immunotoxicity is a pronounced shift in the balance in T helper cell function toward T helper 2 responses at the expense of T helper 1 functions. This bias alters the nature and range of immune responses that can be produced thereby influencing host susceptibility to various diseases. Immunotoxic responses to lead appear to differ across life stages not only quantitatively with regard to dose response, but also qualitatively in terms of the spectrum of immune alterations. Experimental studies in several lab animal species suggest the latter stages of gestation are a period of considerable sensitivity for lead-induced immunotoxicity. This review describes the basic characteristics of lead-induced immunotoxicity emphasizing experimental animal results. It also provides a framework for the consideration of toxicant exposure effects across life stages. The existence of and probable basis for developmental windows of immune hyper-susceptibility are presented. Finally, the potential for lead to serve as a perinatal risk factor for childhood asthma as well as other diseases is considered.

Effect of lead exposure on the immune response of some occupationally exposed individuals

Lead is a ubiquitous pollutant in the industrial environment, which poses serious threats to human health. In the past 20 years increasing attention has been paid to the effects of lead exposure on health. This toxic metal alters the immune response of animals as well as humans. To study the immunological effects of occupational exposure to lead, we examined lymphocyte proliferation, natural killer (NK) cell cytotoxicity and interferon-gamma production with peripheral blood mononuclear cells (PBMCs) of individuals occupationally exposed to lead. We selected three different groups of individuals exposed to lead: three-wheeler drivers (30), battery workers (34) and silver jewelery makers (20); and unexposed healthy volunteers (30) as control for comparison. Our results indicate that though lymphocyte proliferation to phytohaemagglutinin (PHA) is inhibited in lead exposed individuals as compared with unexposed volunteers, there is no correlation between inhibition of lymphocyte proliferation and blood lead level. NK cell cytotoxicity remains unaffected in individuals exposed to lead as compared with controls. On the other hand, we observed that interferon-gamma (IFN-gamma) was significantly elevated in T cell mitogen, PHA, stimulated PBMCs culture supernatant of lead exposed individuals. We found significant positive correlation between blood lead levels and IFN-gamma produced in culture supernatant on stimulation with PHA. In brief, this study demonstrates that lead can affect the immune response of the occupationally exposed individuals such as three-wheeler drivers, battery reconditioning workers and silver jewelery makers.

Suppression of host resistance to Listeria monocytogenes by acute cold/restraint stress: lack of direct IL-6 involvement

We conducted kinetic studies to evaluate the effects of acute cold/restraint stress (ACRS) on both primary and secondary host resistance to Listeria monocytogenes (LM). The involvement of IL-6 also was investigated using IL-6 knockout (KO) mice on the BALB/c background. ACRS dramatically increased the serum corticosterone levels, indicating that ACRS activated the hypothalamic-pituitary-adrenal (HPA) axis. ACRS significantly inhibited host resistance to LM during a primary but not a secondary LM infection. During the primary infection, ACRS caused a significant delay in clearance of LM, loss of body weight, reduced food/water intake, and elevated levels of pro-inflammatory cytokines (IL-6, IL-1beta, and TNFalpha) and IFNgamma. ACRS IL-6 KO mice showed higher LM burdens than did IL-6 KO controls, suggesting that IL-6 is not required for the ACRS-impairment of host resistance. Elevated levels of IL-1beta and TNFalpha may compensate for the absence of IL-6 and maintain the ACRS-induced impairment, in that the serum and splenic IL-1beta and TNFalpha levels were significantly higher in infected ACRS IL-6 KO mice, but not in control IL-6 KO mice, as compared to respective wild type controls. ACRS appears to inhibit IL-6 independent mechanisms associated with innate immunity and/or the development of adaptive immunity, but these reactions are unable to modulate the more efficient secondary immune responses.