Effects of vanadium upon polyl:C-induced responses in rat lung and alveolar macrophages

Role of Macrophages in Air Pollution Exposure Related Asthma

Asthma is a chronic inflammatory airway disease characterized by variable airflow obstruction, bronchial hyper-responsiveness, and airway inflammation. The chronic inflammation of the airway is mediated by many cell types, cytokines, chemokines, and inflammatory mediators. Research suggests that exposure to air pollution has a negative impact on asthma outcomes in adult and pediatric populations. Air pollution is one of the greatest environmental risks to health, and it impacts the lungs' innate and adaptive defense systems. A major pollutant in the air is particulate matter (PM), a complex component composed of elemental carbon and heavy metals. According to the WHO, 99% of people live in air pollution where air quality levels are lower than the WHO air quality guidelines. This suggests that the effect of air pollution exposure on asthma is a crucial health issue worldwide. Macrophages are essential in recognizing and processing any inhaled foreign material, such as PM. Alveolar macrophages are one of the predominant cell types that process and remove inhaled PM by secreting proinflammatory mediators from the lung. This review focuses on macrophages and their role in orchestrating the inflammatory responses induced by exposure to air pollutants in asthma.

Pituitary Adenylate Cyclase-Activating Polypeptide Reverses Ammonium Metavanadate-Induced Airway Hyperresponsiveness in Rats

The rate of atmospheric vanadium is constantly increasing due to fossil fuel combustion. This environmental pollution favours vanadium exposure in particular to its vanadate form, causing occupational bronchial asthma and bronchitis. Based on the well admitted bronchodilator properties of the pituitary adenylate cyclase-activating polypeptide (PACAP), we investigated the ability of this neuropeptide to reverse the vanadate-induced airway hyperresponsiveness in rats. Exposure to ammonium metavanadate aerosols (5 mg/m³/h) for 15 minutes induced 4 hours later an array of pathophysiological events, including increase of bronchial resistance and histological alterations, activation of proinflammatory alveolar macrophages, and increased oxidative stress status. Powerfully, PACAP inhalation (0.1 mM) for 10 minutes alleviated many of these deleterious effects as demonstrated by a decrease of bronchial resistance and histological restoration. PACAP reduced the level of expression of mRNA encoding inflammatory chemokines (MIP-1α, MIP-2, and KC) and cytokines (IL-1α and TNF-α) in alveolar macrophages and improved the antioxidant status. PACAP reverses the vanadate-induced airway hyperresponsiveness not only through its bronchodilator activity but also by counteracting the proinflammatory and prooxidative effects of the metal. Then, the development of stable analogs of PACAP could represent a promising therapeutic alternative for the treatment of inflammatory respiratory disorders.

Vanadium pentoxide prevents NK-92MI cell proliferation and IFNγ secretion through sustained JAK3 phosphorylation

Vanadium is a major air pollutant with toxic and carcinogenic effects; it also exercises immunosuppressive effects on the adaptive immune response. Its effect on the innate immune response is poorly explored. The aim of this study was to identify if vanadium pentoxide (V2O5) impairs the function of immunoregulatory NK cells and to determine possible mechanisms associated with this effect. Interleukin-2-independent NK-92MI cells were exposed to different V2O5 concentrations for 6, 12, or 24 h periods. Cell proliferation was then evaluated using CFSE staining, apoptosis by Annexin V binding, and necrosis by 7-AAD staining. The release of IL-2, -4, -6, -10, -17A, IFNγ, and TNFα by the cells were assessed using a human CBA kit. Expression of CD45, SOCS1, JAK3, pJAK3, STAT5, pSTAT5, IL-2R, IL-15R, Fas, and FasL in/on the cells was determined by flow cytometry; JAK3 and pJAK3 expression were also evaluated via confocal microscopy. The results indicated that V2O5 could inhibit NK-92MI cell proliferation and induce cell apoptosis in a dose- and time-related manner. V2O5 also inhibited IL-2, IL-10, and IFNγ secretion but mostly only after 24 h of exposure and with primarily the higher doses tested. V2O5 had no effect on expression of JAK3 and STAT5, but did cause an increase in pJAK3 and appeared to lead (trend) to reductions in levels of phosphorylated STAT5. V2O5 increased the expression of IL-2R, IL-15R, Fas, and FasL at concentrations above the 50-100 µM range. V2O5 had no effect on expression of the CD45 membrane phosphatase, but it did cause an increase in the expression of SOCS1. These results indicate that a key toxic effect of V2O5 on NK cells is a dysregulation of signaling pathways mediated by IL-2. These effects could help to explain the previously-reported deleterious effects on innate immune responses of hosts exposed to inhaled V2O5.

Genetic susceptibility to interstitial pulmonary fibrosis in mice induced by vanadium pentoxide (V2O5)

Interstitial lung diseases (ILDs) are characterized by injury, inflammation, and scarring of alveoli, leading to impaired function. The etiology of idiopathic forms of ILD is not understood, making them particularly difficult to study due to the lack of appropriate animal models. Consequently, few effective therapies have emerged. We developed an inbred mouse model of ILD using vanadium pentoxide (V2O5), the most common form of a transition metal found in cigarette smoke, fuel ash, mineral ores, and steel alloys. Pulmonary responses to V2O5, including dose-dependent increases in lung permeability, inflammation, collagen content, and dysfunction, were significantly greater in DBA/2J mice compared to C57BL/6J mice. Inflammatory and fibrotic responses persisted for 4 mo in DBA/2J mice, while limited responses in C57BL/6J mice resolved. We investigated the genetic basis for differential responses through genetic mapping of V2O5-induced lung collagen content in BXD recombinant inbred (RI) strains and identified significant linkage on chromosome 4 with candidate genes that associate with V2O5-induced collagen content across the RI strains. Results suggest that V2O5 may induce pulmonary fibrosis through mechanisms distinct from those in other models of pulmonary fibrosis. These findings should further advance our understanding of mechanisms involved in ILD and thereby aid in identification of new therapeutic targets.

Vanadium pentoxide inhalation

Context:

This mini-review describes the toxic effects of vanadium pentoxide inhalation principally in the workplace and associated complications with breathing and respiration. Although there are some material safety data sheets available detailing the handling, hazards and toxicity of vanadium pentoxide, there are only two reviews listed in PubMed detailing its toxicity.

Aim:

To collate information on the consequences of occupational inhalation exposure of vanadium pentoxide on physiological function and wellbeing.

Materials and Methods:

The criteria used in the current mini-review for selecting articles were adopted from proposed criteria in The International Classification of Functioning, Disability and Health. Articles were classified from an acute and chronic exposure and toxicity thrust.

Results:

The lungs are the principal route through which vanadium pentoxide enters the body. It can injure the lungs and bronchial airways possibly involving acute chemical pneumonotis, pulmonary edema and/or acute tracheobronchitis. It may adversely influence cardiac autonomic function. It stimulates the secretion of cytokines and chemokines by hepatocytes and disrupts mitochondria function. It disrupts the permeability of the epithelium and promotes access of inflammatory mediators to the underlying neuronal tissue causing injury and neuronal death. When renal brush border membrane vesicles are exposed to vanadium pentoxide, there is a time-dependent inhibition of citrate uptake and Na⁺ K⁺ ATPase in the membrane possibly contributing to nephrotoxicity. Exposure results in necrosis of spermatogonium, spermatocytes and Sertoli cells contributing to male infertility.

Conclusion:

Vanadium pentoxide certainly has adverse effects on the health and the well-being and measures need to be taken to prevent hazardous exposure of the like.

Photoperiodic regulation of behavioral responses to bacterial and viral mimetics: a test of the winter immunoenhancement hypothesis

Siberian hamsters (Phodopus sungorus) exhibit changes in immune function following adaptation to short photoperiods, including a marked attenuation of energetically expensive thermoregulatory and behavioral responses to gram-negative bacterial infections. Whether this seasonal attenuation of the immune response is idiosyncratic to gram-negative infections or is representative of innate immune responses in general is not known. If seasonal attenuation of responsiveness to infection is indeed driven primarily by anticipation of energetic constraints, then one would predict that responsiveness to all pathogens would be diminished during short days. If, on the other hand, seasonal changes in responsiveness to infection reflect anticipation of specific pathogens that are common at different phases of the annual cycle, then one would expect short photoperiods to attenuate responsiveness to some pathogens and long photoperiods to attenuate responsiveness to others. To resolve this issue, we exposed male Siberian hamsters to either long or short photoperiods for 11 weeks, then examined their behavioral sickness responses to compounds that represent the minimally immunogenic components of gram-negative bacterial (lipopolysaccharide), gram-positive bacterial (muramyl dipeptide), and viral (polyinosinepolycytidylic acid) organisms. Hamsters exhibited anorexic, anhedonic, ponderal, and/or thermoregulatory sickness behaviors to all 3 pathogen mimetics, but in all cases in which sickness responses were evident, they were attenuated in short days. Energetically costly behavioral responses to several distinct classes of infectious organisms are attenuated in anticipation of winter. The data are not consistent with a pathogen-specific seasonal modulation of innate immune responses.

Inhibition of vagally mediated immune-to-brain signaling by vanadyl sulfate speeds recovery from sickness

To the ill patient with diabetes, the behavioral symptoms of sickness such as fatigue and apathy are debilitating and can prevent recuperation. Here we report that peripherally administered insulin-like growth factor 1 (IGF-1) attenuates LPS-dependent depression of social exploration (sickness) in nondiabetic (db/+) but not in diabetic (db/db) mice. We show that the insulin/IGF-1 mimetic vanadyl sulfate (VS) is effective at augmenting recovery from sickness in both db/+ and db/db mice. Specifically, peak illness was reached at 2 h for both VS and control animals injected with LPS, and VS mice recovered 50% faster than non-VS-treated animals. Examination of the mechanism of VS action in db/+ mice showed that VS paradoxically augmented peritoneal macrophage responsivity to LPS, increasing both peritoneal and ex vivo macrophage production of IL-1beta and IL-6 but not TNF-alpha. The effects of VS in promoting recovery from sickness were not restricted to LPS, because they were also observed after direct administration of IL-1beta. To explore the possibility that VS impairs immune-to-brain communication via vagal afferents, the vagally mediated satiety-inducing effects of cholecystokinin 8 were tested in db/+ mice. Cholecystokinin decreased food intake in saline-injected mice but not in VS-treated mice. VS also inhibited LPS-dependent up-regulation of IL-1beta and IL-6 mRNA in the brain, while increasing by 50% the cerebral expression of transcripts of the specific antagonist of IL-1 receptors IL-1RA and IL-1R2. Taken together, these data indicate that VS improves recovery from LPS-induced sickness by blocking vagally mediated immune-to-brain signaling and by up-regulating brain expression of IL-1beta antagonists.

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.

Vanadate induction of NF-kappaB involves IkappaB kinase beta and SAPK/ERK kinase 1 in macrophages

The present studies investigated the signaling pathways of vanadate, a vanadium ion with +5 oxidation state, to activate NF-kappaB transcription factor, a pivotal regulator of inflammatory responses. Treatment of macrophages with vanadate results in the activation of both NF-kappaB and c-Jun N-terminal kinase (JNK). The activity of a recently identified cellular kinase, IkappaB kinase-beta (IKKbeta), was significantly elevated concomitant with the increased degradation of IkappaBalpha and enhanced NF-kappaB activity in cells exposed to vanadate. To determine whether the IKK pathway and JNK pathway are interconnected or bifurcate upon vanadate stimulation, cells were transfected with either a kinase inactive form of IKKbeta or a kinase inactive form of SAPK/ERK kinase 1 (SEK1). Inactive IKKbeta was able to block vanadate-induced degradation of IkappaBalpha, yet it was unable to influence the activation of JNK by vanadate. Conversely, blockage of JNK activation by transfection of a kinase-inactive form of SEK1 resulted in partially inhibition of vanadate-induced IkappaBalpha degradation. Both vanadate-induced degradation of IkappaBalpha and activation of JNK were potently inhibited by pretreatment of cells with N-acetylcysteine or dimercaprol. These results demonstrate that early activation of stress kinases or change of cellular redox states plays a key role in vanadate-induced activation of NF-kappaB and JNK.

Vanadium stimulates immunological responses of chicks

In a continuation of studies on the interaction of dietary phosphorus (P) and vanadium (V) levels, studies have directed toward an examination of this interaction on the immune system of chicks. Antibody titers to sheep red blood cells (SRBC) were increased at 7 days post-inoculation (PI) by as little as 10 mg V/kg diet in the P-deficient group, while 50 mg V/kg was required in the P-supplemented group. At 14 days PI, only the 50 mg V/kg was significantly higher in both P-deficient and P-supplemented groups. At 21 days PI, vanadium had no significant effect. P-deficiency resulted in a decrease in the percentage of phagocytic macrophages obtained from the abdominal cavity and a decrease in the number of intracytoplasmic SRBC per phagocytic macrophage. These two criteria were increased by vanadium in both the P-deficient and P-supplemented animals. In P-supplemented animals, the CD4/CD8 ratios of lymphocytes obtained from the blood and spleen were increased by the inclusion of 50 mg V/kg diet. The IL-1-like activity of macrophage supernatants was not significantly affected by dietary V, but IL-6 activity was increased. Densitometric analysis of lysates of macrophages isolated from control and V-fed chicks for anti-protein-tyrosinephosphate (PTP) bands indicate that dietary V increased PTP. While the evidence is not clear that there is a P x V interaction in the immune system studies, it is clear that dietary V at the levels used results in a positive immune response of chicks, possibly mediated through increased PTP.

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

Soluble and insoluble hexavalent chromium (Cr6+) agents are concomitantly released with ozone (O3) during welding. Although pulmonary/immunologic implications from exposure to each agent individually have been investigated, the effects from simultaneous exposure, as occurs under actual working conditions, are unclear. To investigate immunomodulatory effects of inhaled Cr6+, F-344 rats were exposed for 5 h/day, 5 days/week for 2 or 4 weeks to atmospheres containing soluble potassium chromate (K2CrO4) or insoluble barium chromate (BaCrO4), each alone at 360 micrograms Cr/m3 or in combination with 0.3 ppm O3. One day after the final exposure, rats were euthanized, their lungs were lavaged, and pulmonary macrophages (PAM) were recovered for assessment of basal and inducible functions. Rats inhaling K2CrO4-containing atmospheres had greater levels of total recoverable cells, neutrophils, and monocytes in bronchopulmonary lavage compared to rats exposed to insoluble Cr6+ atmospheres, O3 alone, or air; these rats also had a reduced percentage of PAM, although total PAM levels remained unaffected. Although Cr exposure-related changes in PAM functionality were evident, any dependence upon Cr solubility was variable. K2CrO4-containing atmospheres modulated PAM-inducible interleukins-1 and -6, and tumor necrosis factor-alpha production to a greater degree than those containing BaCrO4. Conversely, BaCrO4-containing atmospheres affected PAM basal nitric oxide production and interferon-gamma-primed/zymosan-stimulated reactive oxygen intermediate production to a greater extent than did those containing K2CrO4. In none of the PAM assays did co-inhalation of O3 result in a modulation of the effects obtained with either Cr6+ compound itself. The results indicate that, while immunomodulatory effects of inhaled Cr6+ upon PAM are related to particle solubility, the co-inhalation of O3 apparently does not cause further modifications of the metal-induced effects.