Immunotoxicologic effects of inhaled chromium: role of particle solubility and co-exposure to ozone

Relationship between systemic inflammation and lung injury induced by chromate exposure: A cross-sectional study in workers

Hexavalent chromium [Cr(VI)] compounds, known as "Group I Human Carcinogen" and "Category I Respiratory Sensitizer", posed great challenges to the respiratory system. A cross-sectional study was undertaken among chromate workers. Serum club cell protein 16 (CC16) and soluble urokinase-type plasminogen activator receptor (suPAR) were measured using ELISA. Thirteen macrophage-related mediators were tested using cytometric bead array. After controlling for sex, age, smoking status, drinking status and BMI, each increase of one-unit of Ln-transformed blood Cr was related to the increase of IL-1beta [Beta (95% CI), 7.22(1.14, 13.29)%, P = 0.021], IL-23 [8.5(1.15, 15.85)%, P = 0.021], IFN-gamma [3.14(0.15, 6.13)%, P = 0.040], and suPAR [9.31(2.5, 16.12) %, P = 0.008], as well as the increase of CC16 by 3.88(0.42, 7.34) % (P = 0.029). Moreover, these inflammatory mediators played an mediation role in the rise of CC16 caused by Cr(VI). The exposure-response curve analysis revealed a substantial nonlinear association of IFN-gamma and suPAR with CC16, thus the mediation effect of INF-gamma and suPAR required cautious interpretation. The positive connection between macrophage-related mediators was stronger in the high exposure group than in the low exposure group, suggesting that high concentration of chromate might promote a complex interplay within the immune system.

The regulatory role of COX-2 in the interaction between Cr(VI)-induced endoplasmic reticulum stress and autophagy in DF-1 cells

Hexavalent chromium (Cr(VI)) is a common environmental pollutant. Exposure of Cr(VI) can lead to cell autophagy, but the preventive measures for diminishing Cr(VI)-induced autophagy need further study. COX-2 can be induced by several heavy metals and can lead to endoplasmic reticulum (ER) stress and autophagy; thus, COX-2, ER stress, and autophagy may be related. This study mainly investigated the role of COX-2 in the eIF2α-ATF4 pathway, which is a major pathway in cell autophagy. In this study, Cr(VI) was used as a xenobiotic to determine changes in the parameters of ER stress, autophagy, and COX-2 levels. At the same time, a clear contrast was obtained by assigning positive and negative controls of ER stress and autophagy. The results showed that during Cr(VI) invasion, the parameters of ER stress and autophagy (such as BiP, PERK, p62, LC3-II, and mTOR) were enhanced, similarly to the positive control of ER stress and/or the autophagy controls. Such enhancement is a protective mechanism for cell survival. Additionally, the COX-2 levels increased. Moreover, when COX-2 was inhibited, the PERK level remained high, whereas the LC3-II level decreased. This finding suggests that COX-2 specifically affects the interaction between ER stress and autophagy. Notably, this study reveals that Cr(VI) can induce ER stress and autophagy in DF-1 cells and that COX-2 plays an essential role in the interaction between ER stress and autophagy.

Assessment of immunotoxicity in female Fischer 344/N and Sprague Dawley rats and female B6C3F1 mice exposed to hexavalent chromium via the drinking water

Sodium dichromate dihydrate (SDD), an inorganic compound containing hexavalent chromium (Cr(VI)), is a common environmental contaminant of groundwater sources due to widespread industrial use. There are indications in the literature that Cr(VI) may induce immunotoxic effects following dermal exposure, including acting as both an irritant and a sensitizer; however, the potential immunomodulatory effects of Cr(VI) following oral exposure are relatively unknown. Following the detection of Cr(VI) in drinking water sources, the National Toxicology Program (NTP) conducted extensive evaluations of the toxicity and carcinogenicity of SDD following drinking water exposure, including studies to assess the potential for Cr(VI) to modulate immune function. For the immunotoxicity assessments, female Fischer 344/N (F344/N) and Sprague Dawley (SD) rats and female B₆C₃F₁ mice were exposed to SDD in drinking water for 28 consecutive days and evaluated for alterations in cellular and humoral immune function as well as innate immunity. Rats were exposed to concentrations of 0, 14.3, 57.3, 172, or 516 ppm SDD while mice were exposed to concentrations of 0, 15.6, 31.3, 62.5, 125, or 250 ppm SDD. Final mean body weight and body weight gain were decreased relative to controls in 250 ppm B₆C₃F₁ mice and 516 ppm SD rats. Water consumption was significantly decreased in F344/N and SD rats exposed to 172 and 516 ppm SDD; this was attributed to poor palatability of the SDD drinking water solutions. Several red blood cell-specific parameters were significantly (5-7%) decreased in 250 ppm mice; however, these parameters were unaffected in rats. Sporadic increases in the spleen IgM antibody response to sheep red blood cells (SRBC) were observed, however, these increases were not dose-dependent and were not reproducible. No significant effects were observed in the other immunological parameters evaluated. Overall, exposure to Cr(VI) in drinking water had limited effects on the immune system in both rats and mice.

Characterization of ambient particles size in workplace of manufacturing physical fitness equipments

The manufacturing of fitness equipment involves several processes, including the cutting and punching of iron tubes followed by welding. Welding operations produce hazardous gases and particulate matter, which can enter the alveolar, resulting in adverse health effects. This study sought to verify the particle size distribution and exposure concentrations of atmospheric air samples in various work areas of a fitness equipment manufacturing industry. Observed particle concentrations are presented by area and in terms of relative magnitude: painting (15.58 mg/m(3)) > automatic welding (0.66 mg/m(3)) > manual welding (0.53 mg/m(3)) > punching (0.18 mg/m(3)) > cutting (0.16 mg/m(3)). The concentrations in each of the five work areas were Cinh>Cthor>Cresp. In all areas except the painting area, extra-fine particles produced by welding at high temperatures, and further those coagulated to form larger particles. This study observed bimodal distribution in the size of welding fume in the ranges of 0.7-1 µm and 15-21 µm. Meanwhile, the mass concentrations of particles with different sizes were not consistent across work areas. In the painting area, the mass concentration was higher in Chead>Cth>Calv, but in welding areas, it was found that Calv>Chead>Cth. Particles smaller than 1 µm were primarily produced by welding.

Oxidative stress and reduced responsiveness of challenged circulating leukocytes following pulmonary instillation of metal-rich particulate matter in rats

Welding fume is an exposure that consists of a mixture of metal-rich particulate matter with gases (ozone, carbon monoxide) and/or vapors (VOCs). Data suggests that welders are immune compromised. Given the inability of pulmonary leukocytes to properly respond to a secondary infection in animal models, the question arose whether the dysfunction persisted systemically. Our aim was to evaluate the circulating leukocyte population in terms of cellular activation, presence of oxidative stress, and functionality after a secondary challenge, following welding fume exposure. Rats were intratracheally instilled (ITI) with PBS or 2 mg of welding fume collected from a stainless steel weld. Rats were sacrificed 4 and 24 h post-exposure and whole blood was collected. Whole blood was used for cellular differential counts, RNA isolation with subsequent microarray and Ingenuity Pathway Analysis, and secondary stimulation with LPS utilizing TruCulture technology. In addition, mononuclear cells were isolated 24 h post-exposure to measure oxidative stress by flow cytometry and confocal microscopy. Welding fume exposure had rapid effects on the circulating leukocyte population as identified by relative mRNA expression changes. Instillation of welding fume reduced inflammatory protein production of circulating leukocytes when challenged with the secondary stimulus LPS. The effects were not related to transcription, but were observed in conjunction with oxidative stress. These findings support previous studies of an inadequate pulmonary immune response following a metal-rich exposure and extend those findings showing leukocyte dysfunction occurs systemically.

Efficiency of different respiratory protective devices for removal of particulate and gaseous reactive oxygen species from welding fumes

Ultraviolet (UV) light inherent to welding processes generates ozone (O(3)) with subsequent formation of reactive oxygen species (ROS) through photochemical reactions when UV light is present with O(3). This study aimed to determine the performance of filters used as respiratory protective devices by welding personnel to simultaneously mitigate particulate and gaseous inhalation hazards. Four respiratory protective devices were selected for this study, including a surgical facemask, a cotton-fabric facemask, an activated-carbon facemask, and an N95 respirator. The removal efficiencies for the particulates in welding fumes were all above 98%. For particulate-phase ROS, the removal efficiencies of the different respiratory protective devices ranged from 83.5% to 94.1%; however, the removal efficiencies for gaseous ROS were only 1.3% (active carbon facemask) to 21.1% (N95 respirator). The data indicated that the respiratory protective devices commercially available cannot block the passage of the gas-phase ROS found in welding fumes.

Immunotoxicology of arc welding fume: worker and experimental animal studies

Arc welding processes generate complex aerosols composed of potentially hazardous metal fumes and gases. Millions of workers worldwide are exposed to welding aerosols daily. A health effect of welding that is of concern to the occupational health community is the development of immune system dysfunction. Increased severity, frequency, and duration of upper and lower respiratory tract infections have been reported among welders. Specifically, multiple studies have observed an excess mortality from pneumonia in welders and workers exposed to metal fumes. Although several welder cohort and experimental animal studies investigating the adverse effects of welding fume exposure on immune function have been performed, the potential mechanisms responsible for these effects are limited. The objective of this report was to review both human and animal studies that have examined the effect of welding fume pulmonary exposure on local and systemic immune responses.

Systemic immune cell response in rats after pulmonary exposure to manganese-containing particles collected from welding aerosols

Welding fume inhalation affects the immune system of exposed workers. Manganese (Mn) in welding fume may induce immunosuppressive effects. The goal was to determine if Mn in welding fume alters immunity by reducing the number of circulating total leukocytes and specific leukocyte sub-populations. Sprague-Dawley rats were treated by intratracheal instillation (ITI) with either a single dose (2.00 mg/rat) or repeated doses (0.125 or 2.00 mg/rat for 7 weeks) with welding fumes that contained different levels of Mn. Additional rats were treated by ITI once a week for 7 weeks with the two doses of manganese chloride (MnCl₂). Bronchoalveolar lavage was performed to assess lung inflammation. Also, whole blood was recovered, and the number of circulating total leukocytes, as well as specific lymphocyte subsets, was determined by flow cytometry. The welding fume highest in Mn content significantly increased lung inflammation, injury, and production of inflammatory cytokines and chemokines compared to all other treatment groups. In addition, the same group expressed significant decreases in the number of circulating CD4⁺ and CD8⁺ T-lymphocytes after a single exposure, and significant reductions in the number of circulating total lymphocytes, primarily CD4⁺ and CD8⁺ T-lymphocytes, after repeated exposures (compared to control values). Repeated MnCl₂ exposure led to a trend of a reduction (but not statistically significant) in circulating total lymphocytes, attributable to the changes in the CD4⁺ T-lymphocyte population levels. The welding fume with the lower concentration of Mn had no significant effect on the numbers of blood lymphocytes and lymphocyte subsets compared to control values. Evidence from this study indicates that pulmonary exposure to certain welding fumes cause decrements in systemic immune cell populations, specifically circulating T-lymphocytes, and these alterations in immune cell number are not dependent exclusively on Mn, but likely a combination of other metals present in welding fume.

Pulmonary toxicity and extrapulmonary tissue distribution of metals after repeated exposure to different welding fumes

Welders are exposed to fumes with different metal profiles. The goals of this study were to compare lung responses in rats after treatment with chemically different welding fumes and to examine the extrapulmonary fate of metals after deposition in the lungs. Rats were treated by intratracheal instillation (0.5 mg/rat, once a week for 7 weeks) with gas metal arc-mild steel (GMAW-MS) or manual metal arc-hardsurfacing (MMAW-HS) welding fumes. Controls were treated with saline. At 1, 4, 35, and 105 days after the last treatment, lung injury and inflammation were measured, and elemental analysis of different organs was determined to assess metal clearance. The MMAW-HS fume was highly water-soluble and chemically more complex with higher levels of soluble Mn and Cr compared to the GMAW-MS fume. Treatments with the GMAW-MS fume had no effect on toxicity when compared with controls. The MMAW-HS fume induced significant lung damage early after treatment that remained elevated until 35 days. Metals associated with each fume sample was cleared at different rates from the lungs. Mn was cleared from the lungs at a faster rate and to a greater extent compared to the other metals over the 105-day recovery period. Mn and Cr in the MMAW-HS fume translocated from the respiratory tract and deposited in other organs. Importantly, increased deposition of Mn, but not other metals, was observed in discrete brain regions, including dopamine-rich areas (e.g., striatum and midbrain).

Effects of metal compounds with distinct physicochemical properties on iron homeostasis and antibacterial activity in the lungs: chromium and vanadium

In situ reactions of metal ions or their compounds are important mechanisms by which particles alter lung immune responses. The authors hypothesized that major determinants of the immunomodulatory effect of any metal include its redox behavior/properties, oxidation state, and/or solubility, and that the toxicities arising from differences in physicochemical parameters are manifest, in part, via differential shifts in lung iron (Fe) homeostasis. To test the hypotheses, immunomodulatory potentials for both pentavalent vanadium (VV; as soluble metavanadate or insoluble vanadium pentoxide) and hexavalent chromium (CrVI; as soluble sodium chromate or insoluble calcium chromate) were quantified in rats after inhalation (5h/day for 5 days) of each at 100 microg metal/m3. Differences in effects on local bacterial resistance between the two VV, and between each CrVI, agents suggested that solubility might be a determinant of in situ immunotoxicity. For the soluble forms, VV had a greater impact on resistance than CrVI, indicating that redox behavior/properties was likely also a determinant. The soluble VV agent was the strongest immunomodulant. Regarding Fe homeostasis, both VV agents had dramatic effects on airway Fe levels. Both also impacted local immune/airway epithelial cell Fe levels in that there were significant increases in production of select cytokines/chemokines whose genes are subject to regulation by HIF-1 (whose intracellular longevity is related to cell Fe status). Our findings contribute to a better understanding of the role that metal compound properties play in respiratory disease pathogenesis and provide a rationale for differing pulmonary immunotoxicities of commonly encountered ambient metal pollutants.

Lung inflammation, injury, and proliferative response after repetitive particulate hexavalent chromium exposure

BACKGROUND

Chronic inflammation is implicated in the development of several human cancers, including lung cancer. Certain particulate hexavalent chromium [Cr(VI)] compounds are well-documented human respiratory carcinogens that release genotoxic soluble chromate and are associated with fibrosis, fibrosarcomas, adenocarcinomas, and squamous cell carcinomas of the lung. Despite this, little is known about the pathologic injury and immune responses after repetitive exposure to particulate chromates.

OBJECTIVES

In this study we investigated the lung injury, inflammation, proliferation, and survival signaling responses after repetitive exposure to particulate chromate.

METHODS

BALB/c mice were repetitively treated with particulate basic zinc chromate or saline using an intranasal exposure regimen. We assessed lungs for Cr(VI)-induced changes by bronchoalveolar lavage, histologic examination, and immunohistochemistry.

RESULTS

Single exposure to Cr(VI) resulted in inflammation of lung tissue that persists for up to 21 days. Repetitive Cr(VI) exposure induced a neutrophilic inflammatory airway response 24 hr after each treatment. Neutrophils were subsequently replaced by increasing numbers of macrophages by 5 days after treatment. Repetitive Cr(VI) exposure induced chronic peribronchial inflammation with alveolar and interstitial pneumonitis dominated by lymphocytes and macrophages. Moreover, chronic toxic mucosal injury was observed and accompanied by increased airway pro-matrix metalloprotease-9. Injury and inflammation correlated with airways becoming immunoreactive for phosphorylation of the survival signaling protein Akt and the proliferation marker Ki-67. We observed a reactive proliferative response in epithelial cells lining airways of chromate-exposed animals.

CONCLUSIONS

These data illustrate that repetitive exposure to particulate chromate induces chronic injury and an inflammatory microenvironment that may promote Cr(VI) carcinogenesis.

Lung injury, inflammation and Akt signaling following inhalation of particulate hexavalent chromium

Certain particulate hexavalent chromium [Cr(VI)] compounds are human respiratory carcinogens that release genotoxic soluble chromate, and are associated with fibrosis, fibrosarcomas, adenocarcinomas and squamous cell carcinomas of the lung. We postulate that inflammatory processes and mediators may contribute to the etiology of Cr(VI) carcinogenesis, however the immediate (0-24 h) pathologic injury and immune responses after exposure to particulate chromates have not been adequately investigated. Our aim was to determine the nature of the lung injury, inflammatory response, and survival signaling responses following intranasal exposure of BALB/c mice to particulate basic zinc chromate. Factors associated with lung injury, inflammation and survival signaling were measured in airway lavage fluid and in lung tissue. A single chromate exposure induced an acute immune response in the lung, characterized by a rapid and significant increase in IL-6 and GRO-alpha levels, an influx of neutrophils, and a decline in macrophages in lung airways. Histological examination of lung tissue in animals challenged with a single chromate exposure revealed an increase in bronchiolar cell apoptosis and mucosal injury. Furthermore, chromate exposure induced injury and inflammation that progressed to alveolar and interstitial pneumonitis. Finally, a single Cr(VI) challenge resulted in a rapid and persistent increase in the number of airways immunoreactive for phosphorylation of the survival signaling protein Akt, on serine 473. These data illustrate that chromate induces both survival signaling and an inflammatory response in the lung, which we postulate may contribute to early oncogenesis.

Immunomodulatory effects of seabuckthorn (Hippophae rhamnoides L.) against chromium (VI) induced immunosuppression

The present study reports the immunomodulatory effects of seabuckthorn (Hippophae rhamnoides L.) leaf extract on cellular and humoral immune response by studying delayed-type hypersensitivity response, IL-2, IL-4 and gamma-IFN levels and antibody titres in chromium-induced immunosuppressed animals. Oral feeding of chromium (30 mg/kg bw) significantly inhibited antibody production and S-RBC induced delayed-type hypersensitivity response. Administration of leaf extract (100 mg/kg bw) along with chromium significantly inhibited chromium-induced immunosuppression. To understand the immunomodulatory mechanism of leaf extract, in vitro studies were carried out using rat lymphocytes. Addition of chromium resulted in a significant decrease in lymphocyte size and increased ROS generation. The leaf extract of seabuckthorn significantly inhibited chromium-induced reactive oxygen species (ROS) generation and maintained the cell size identical to that of control cells. Chromium treatment markedly inhibited the mitochondrial transmembrane potential by larger lymphocytes in particular, while the leaf extract restored the same significantly. Chromium also inhibited significantly concanavalin A (ConA) induced IL-2, IL-4 and gamma-IFN production in rat lymphocytes. The leaf extract (100 microg/ml) alone stimulated IL-2 and gamma-IFN production even in the absence of ConA and also inhibited chromium-induced decline in IL-2 and gamma-IFN production but it did not change IL-4 production. These observations suggest that the leaf extract of seabuckthorn has significant immunomodulatory activity and specifically activates the cell-mediated immune response.

Changes of 8-OH-dG levels in DNA and its base excision repair activity in rat lungs after inhalation exposure to hexavalent chromium

According to the toxicological and epidemiological studies, hexavalent chromium (Cr) is associated with increase of lung cancer risk. Genotoxic effects, such as chromosomal aberrations, and cellular oxidative DNA damage by reactive oxygen species produced by hexavalent Cr exposure may play an important role in its carcinogenesis. To clarify whether reactive oxygen species are involved in its mechanism, we examined the levels of 8-hydroxydeoxyguanine (8-OH-dG) and its base excision repair activities in the lung tissues of rats that repeatedly inhaled a sodium chromate solution mist for 1, 2, and 3 weeks. The levels of 8-OH-dG increased significantly in the lung tissues of the rats exposed for 1 week at the low concentration (0.18 mg/m(3), P<0.05), as compared with the controls. However, there was no difference in the 8-OH-dG levels at the higher concentration or with more than 2 weeks of exposure. The 8-OH-dG repair activities decreased in a dose-dependent manner during 2 weeks of exposure, on the contrary they recovered at 3 weeks of repeated exposure. These results suggest that the DNA damage caused by hexavalent Cr inhalation is induced by the generation of reactive oxygen species and by inhibition of base excision repair activity during the earlier phase of exposure. However, the 8-OH-dG levels and its repair activities recovered to the level of the controls in the latter inhalation exposure period.

Health effects of welding

Many of the epidemiology studies performed are difficult to compare because of differences in worker populations, industrial settings, welding techniques, duration of exposure, and other occupational exposures besides welding fumes. Some studies were conducted in carefully controlled work environments, others during actual workplace conditions, and some in laboratories. Epidemiology studies have shown that a large number of welders experience some type of respiratory illness. Respiratory effects seen in full-time welders have included bronchitis, airway irritation, lung function changes, and a possible increase in the incidence of lung cancer. Pulmonary infections are increased in terms of severity, duration, and frequency among welders. Although epidemiological studies have demonstrated an increase in pulmonary illness after exposure to welding fumes, little information of the causality, dose-response, and possible underlying mechanisms regarding the inhalation of welding fumes exists. Even less information is available about the neurological, reproductive, and dermal effects after welding fume exposure. Moreover, carcinogenicity and short-term and long-term toxicology studies of welding fumes in animals are lacing or incomplete. Therefore, an understanding of possible adverse health effects of exposure to welding fumes is essential to risk assessment and the development of prevention strategies and will impact a large population of workers.

Impact of coexposure to ozone on the carcinogenic potential of inhaled chromium. 1. effects on retention and on extra- and intracellular distribution

A health hazard to welders is development of lung cancer. It is believed that this is likely due, in part, to the presence in welding fumes of several hexavalent chromium (Cr[VI]) species, whose solubility depends primarily on which process (i.e., manual metal arc verus metal-inert gas) is used. However, inhalation of Cr alone is uncommon in this setting. Thus, an examination of potential contributions from other coinhalants in creating or enhancing conditions whereby inhaled fume-associated Cr (primarily the insoluble forms) may initiate cancer is critical to increasing our understanding and preventing this particular occupational disease. One major chemical species formed and released during welding is ozone (O3). Though implications of adverse pulmonary effects from individual exposure to Cr or O3 have been investigated, those from simultaneous exposure are unclear. To begin to address whether the carcinogenic potential of insoluble Cr[VI] agents might be enhanced in hosts inhaling mixtures of Cr and O3 versus Cr alone, analyses of total lung Cr burden, Cr retention in lung epithelium and interstitium, and potential shifts in lung cell distribution of Cr from the cytoplasm to nuclei were undertaken in F-344 rats exposed nose-only (5 h/d, 5 d/wk for up to 48 wk) to an extrapolated occupationally relevant level of Cr (360 micrograms Cr/m3 as calcium chromate) alone and in combination with 0.3 ppm O3. Overall, there was only a nominal effect from O3 on Cr retention or on distribution of Cr particles among extracellular sites and within lung cells. However, there were O3-related effects upon mechanisms for clearing the Cr from the deep lung, specifically at the levels of particle uptake and postphagocytic/endocytic processing by macrophages. This O3 exposure-related shift in normal pulmonary clearance might potentially increase the health risk in workers exposed to other insoluble or poorly soluble carcinogenic Cr compounds.

Chromate-induced epimutations in mammalian cells

Epigenetic gene silencing by aberrant DNA methylation of gene promoter regions is a nonmutagenic but heritable epigenetic mechanism that may mistakenly cause the silencing of important cancer-related tumor suppressor genes. Using a transgenic, V79-derived, mammalian cell line (G12) that contains a bacterial gpt reporter gene in its DNA, we can study carcinogen-induced gene inactivation by mutagenic as well as epigenetic DNA methylation mechanisms. Whereas numerous carcinogens have previously been shown to be mutagenic in these cells, a few carcinogens, including nickel, diethylstilbestrol, and X-rays, are also capable of silencing the G12 cell gpt transgene by aberrant DNA methylation. Here we report for the first time that carcinogenic potassium chromate salts can also induce aberrant DNA methylation in this system. In contrast insoluble barium chromate produced significant level of mutations in these cells but did not cause DNA methylation changes associated with transgene expression.

Anti-oxidant and immunomodulatory properties of seabuckthorn (Hippophae rhamnoides)--an in vitro study

This study was designed to determine the anti-oxidant and immunomodulatory properties of seabuckthorn (Hippophae rhamnoides) using lymphocytes as a model system. Chromium(VI) as potassium dichromate was used to induce oxidative damage. The production of free radicals by chromium and the ability of alcoholic leaf and fruit extracts of seabuckthorn to inhibit the oxidative damage induced by chromium was investigated. Addition of chromium (10 microg/ml) to the cells resulted in enhanced cytotoxicity, apoptosis, free radical production and decreased glutathione (reduced) levels. Chromium also caused a significant inhibition of lymphocyte proliferation induced by both lipopolysaccharide and concanavalin A. Alcoholic extracts of leaves and fruits of seabuckthorn at a concentration of 500 microg/ml were found to inhibit chromium-induced free radical production, apoptosis, DNA fragmentation and restored the anti-oxidant status to that of control cells. In addition, these extracts also were able to arrest the chromium-induced inhibition of lymphocyte proliferation. These observations suggest that the alcoholic extracts of leaves and fruits of seabuckthorn have marked cytoprotective properties, which could be attributed to the anti-oxidant activity.

Mechanisms of chromium toxicity, carcinogenicity and allergenicity: review of the literature from 1985 to 2000

Laboratory and clinical reports about the pathogenesis of the carcinogenicity and allergenicity of chromium compounds published between 1985 and 2000 have been reviewed as a basis for consideration of the pathogenetic mechanisms involved. There is good evidence from the clinic and the laboratory that Cr[VI] is the ion responsible for most of the toxic actions, although much of the underlying molecular damage may be due to its intracellular reduction to the even more highly reactive and short-lived chemical species Cr[III] and Cr[V]. Exposure to Cr[VI] can result in various point mutations in DNA and to chromosomal damage, as well as to oxidative changes in proteins and to adduct formation. The relative importance of these effects of chromium ions and of the free oxidising radicals they may generate in the body in causing tumours and allergic sensitisation remain to be demonstrated. Biochemical studies of the DNA-damaging effects and of the pathogenesis of the allergic reactions to chromium ions have not kept up with advances in understanding of the molecular basis of the effects of other carcinogens and allergens.

Ozone-induced modulation of cell-mediated immune responses in the lungs

Most pulmonary immunotoxicology studies of ambient pollutants have been broadly designed to discern if overall humoral or cell-mediated immunity (CMI) was altered; few have assessed effects on particular aspects of immune function. We hypothesized that effects from ozone (O3) exposure on pulmonary CMI are linked in part to changes in local immune cell capacities to form and/or to interact with immunoregulatory cytokines. Rats exposed to 0.1 or 0.3 ppm O3 4 h/day 5 days/week, for 1 or 3 weeks were assessed for resistance to, and pulmonary clearance of, a subsequent Listeria monocytogenes challenge. In situ cytokine release and immune cell profiles were also analyzed at different stages of the antilisterial response. Although O3 exposure modulated CMI, effects were not consistently concentration- or duration-dependent. Exposure did not effect cumulative mortality from infection, but induced concentration-related effects upon morbidity onset and persistence. All 1-week exposed rats had listeric burdens trending higher than controls; 0.3 ppm rats displayed continual burden increases rather than any onset of resolution. Rats exposed for 3 weeks had no O3-related changes in clearance. No exposure-related effect on neutrophil or pulmonary macrophage (PAM) numbers or percentages was noted. Bacterial burden analyses with respect to cell type showed that Listeria:PAM ratios in 0.3 ppm rats ultimately became greatest compared to all other rats. In situ IL-1alpha and TNFalpha levels were consistently higher in O3-exposed rats. All rats displayed increasing in situ IFNgamma levels as infection progressed, but no constant relationship was evident between IFNgamma and initial IL-1alpha/TNFalpha levels in O3-exposed hosts. It seems that short-term (i.e., 1 week) repeated O3 exposures imparted more effects upon CMI than a more prolonged (i.e., 3 week) regimen, with effects manifesting at the level of the PAM and in the cytokine network responsible for immunoactivation.

Effect of Kombucha tea on chromate(VI)-induced oxidative stress in albino rats

The effect of Kombucha tea (KT) on oxidative stress induced changes in rats subjected to chromate treatment are reported. KT feeding alone did not show any significant change in malondialdehyde (MDA) and reduced glutathione (GSH) levels, but did enhance humoral response and delayed type of hypersensitivity (DTH) response appreciably over control animals. Chromate treatment significantly enhanced plasma and tissue MDA levels, decreased DTH response considerably, enhanced glutathione peroxidase and catalase activities; however, no change in GSH, superoxide dismutase and antibody titres was noticed. KT feeding completely reversed the chromate-induced changes. These results show that Kombucha tea has potent anti-oxidant and immunopotentiating activities.